Quantum-Si (QSI) 10-Q 15 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 09, 2021
Entity Listings [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Document Transition Report	false
Entity File Number	001-39486
Entity Registrant Name	QUANTUM-SI INCORPORATED
Entity Central Index Key	0001816431
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	85-1388175
Entity Address, Address Line One	530 Old Whitfield Street
Entity Address, City or Town	Guilford
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06437
City Area Code	203
Local Phone Number	458-7100
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Class A Common Stock [Member]
Entity Listings [Line Items]
Title of 12(b) Security	Class A common stock, $0.0001 per share
Trading Symbol	QSI
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		117,478,783
Class B Common Stock [Member]
Entity Listings [Line Items]
Entity Common Stock, Shares Outstanding		19,937,500
Redeemable Warrants [Member]
Entity Listings [Line Items]
Title of 12(b) Security	Redeemable warrants, each whole warrant exercisable for one share of Class A common stock, each at an exercise price of $11.50 per share
Trading Symbol	QSIAW
Security Exchange Name	NASDAQ

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 62,103	$ 36,910
Marketable securities	438,102	0
Prepaid expenses and other current assets	4,997	948
Total current assets	505,202	37,858
Property and equipment, net	4,207	1,996
Other assets	117	0
Other assets - related party	0	738
Total assets	509,526	40,592
Current Liabilities:
Accounts payable	3,172	1,329
Accrued expenses and other current liabilities	4,024	1,425
Total current liabilities	7,196	2,754
Long-term liabilities:
Warrant liabilities	8,176	0
Notes payable	0	1,749
Other long-term liabilities	239	0
Total liabilities	15,611	4,503
Commitments and contingencies (Note 14)
Convertible preferred stock
Convertible preferred stock (Series A, B, C, D, and E) $0.0001 par value with an aggregate liquidation preference of $0 and $216 as of September 30, 2021 and December 31, 2020, respectively; 0 and 92,078,549 shares authorized as of September 30, 2021 and December 31, 2020, respectively; 0 and 90,789,268 shares issued and outstanding as of September 30, 2021 and December 31, 2020, respectively	0	195,814
Stockholders' equity (deficit)
Additional paid-in capital	731,711	12,517
Accumulated deficit	(237,810)	(172,243)
Total stockholders' equity (deficit)	493,915	(159,725)
Total liabilities, convertible preferred stock and stockholders' equity (deficit)	509,526	40,592
Class A Common Stock [Member]
Stockholders' equity (deficit)
Common Stock	12	1
Class B Common Stock [Member]
Stockholders' equity (deficit)
Common Stock	$ 2	$ 0

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Convertible preferred stock
Convertible preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Convertible preferred stock, aggregate liquidation preference	$ 0	$ 216
Convertible preferred stock, shares authorized (in shares)	0	92,078,549
Convertible preferred stock, shares issued (in shares)	0	90,789,268
Convertible preferred stock, shares outstanding (in shares)	0	90,789,268
Class A Common Stock [Member]
Stockholders' equity (deficit)
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	600,000,000	90,000,000
Common stock, shares issued (in shares)	116,717,990	5,378,287
Common stock, shares outstanding (in shares)	116,717,990	5,378,287
Class B Common Stock [Member]
Stockholders' equity (deficit)
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	27,000,000	0
Common stock, shares issued (in shares)	19,937,500	0
Common stock, shares outstanding (in shares)	19,937,500	0

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Operating expenses:
Research and development	$ 11,104	$ 6,655	$ 32,190	$ 21,174
General and administrative	12,989	1,631	34,211	5,157
Sales and marketing	1,082	266	2,717	825
Total operating expenses	25,175	8,552	69,118	27,156
Loss from operations	(25,175)	(8,552)	(69,118)	(27,156)
Interest expense	0	(4)	(5)	(5)
Dividend income	739	2	741	95
Change in fair value of warrant liabilities	6,975	0	3,442	0
Other (expense), net	(630)	(3)	(627)	(2)
Loss before provision for income taxes	(18,091)	(8,557)	(65,567)	(27,068)
Provision for income taxes	0	0	0	0
Net loss	(18,091)	(8,557)	(65,567)	(27,068)
Comprehensive loss	$ (18,091)	$ (8,557)	$ (65,567)	$ (27,068)
Net loss per common share attributable to common stockholders, basic (in dollars per share)	$ (0.13)	$ (1.60)	$ (1.09)	$ (5.06)
Net loss per common share attributable to common stockholders, diluted (in dollars per share)	$ (0.13)	$ (1.60)	$ (1.09)	$ (5.06)
Weighted-average shares used to compute net loss per share attributable to common stockholders, basic (in shares)	136,456,848	5,360,497	60,104,891	5,350,771
Weighted-average shares used to compute net loss per share attributable to common stockholders, diluted (in shares)	136,456,848	5,360,497	60,104,891	5,350,771

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' (DEFICIT) - USD ($) $ in Thousands	Common Stock [Member]Class A Common Stock [Member]	Common Stock [Member]Class B Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Total
Balance at Dec. 31, 2019					$ 160,555
Balance (in shares) at Dec. 31, 2019					84,201,570
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of Series E convertible preferred stock, net of issuance costs					$ 10,288
Issuance of Series E convertible preferred stock, net of issuance costs (in shares)					1,923,519
Balance at Mar. 31, 2020					$ 170,843
Balance (in shares) at Mar. 31, 2020					86,125,089
Balance at Dec. 31, 2019	$ 1	$ 0	$ 10,530	$ (135,630)	$ (125,099)
Balance (in shares) at Dec. 31, 2019	5,263,403	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ 0	$ 0	0	(10,314)	(10,314)
Issuance of series E convertible preferred stock, net of issuance costs	$ 0	$ 0	0	0	0
Issuance of series E convertible preferred stock, net of issuance costs (in shares)	0	0
Common stock issued upon exercise of stock options	$ 0	$ 0	18	0	18
Common stock issued upon exercise of stock options (in shares)	87,796	0
Stock-based compensation expense	$ 0	$ 0	642	0	642
Balance at Mar. 31, 2020	$ 1	$ 0	11,190	(145,944)	(134,753)
Balance (in shares) at Mar. 31, 2020	5,351,199	0
Balance at Dec. 31, 2019					$ 160,555
Balance (in shares) at Dec. 31, 2019					84,201,570
Balance at Sep. 30, 2020					$ 170,831
Balance (in shares) at Sep. 30, 2020					86,125,089
Balance at Dec. 31, 2019	$ 1	$ 0	10,530	(135,630)	$ (125,099)
Balance (in shares) at Dec. 31, 2019	5,263,403	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss					(27,068)
Balance at Sep. 30, 2020	$ 1	$ 0	12,173	(162,698)	(150,524)
Balance (in shares) at Sep. 30, 2020	5,366,827	0
Balance at Mar. 31, 2020					$ 170,843
Balance (in shares) at Mar. 31, 2020					86,125,089
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of Series E convertible preferred stock, net of issuance costs					$ (12)
Issuance of Series E convertible preferred stock, net of issuance costs (in shares)					0
Balance at Jun. 30, 2020					$ 170,831
Balance (in shares) at Jun. 30, 2020					86,125,089
Balance at Mar. 31, 2020	$ 1	$ 0	11,190	(145,944)	$ (134,753)
Balance (in shares) at Mar. 31, 2020	5,351,199	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ 0	$ 0	0	(8,197)	(8,197)
Issuance of series E convertible preferred stock, net of issuance costs	$ 0	$ 0	0	0	0
Issuance of series E convertible preferred stock, net of issuance costs (in shares)	0	0
Stock-based compensation expense	$ 0	$ 0	466	0	466
Balance at Jun. 30, 2020	$ 1	$ 0	11,656	(154,141)	(142,484)
Balance (in shares) at Jun. 30, 2020	5,351,199	0
Balance at Sep. 30, 2020					$ 170,831
Balance (in shares) at Sep. 30, 2020					86,125,089
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ 0	$ 0	0	(8,557)	$ (8,557)
Common stock issued upon exercise of stock options	$ 0	$ 0	24	0	24
Common stock issued upon exercise of stock options (in shares)	15,628	0
Stock-based compensation expense	$ 0	$ 0	493	0	493
Balance at Sep. 30, 2020	$ 1	$ 0	12,173	(162,698)	(150,524)
Balance (in shares) at Sep. 30, 2020	5,366,827	0
Balance at Dec. 31, 2020					$ 195,814
Balance (in shares) at Dec. 31, 2020					90,789,268
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of Series E convertible preferred stock, net of issuance costs					$ (4)
Issuance of Series E convertible preferred stock, net of issuance costs (in shares)					0
Balance at Mar. 31, 2021					$ 195,810
Balance (in shares) at Mar. 31, 2021					90,789,268
Balance at Dec. 31, 2020	$ 1	$ 0	12,517	(172,243)	$ (159,725)
Balance (in shares) at Dec. 31, 2020	5,378,287	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ 0	$ 0	0	(11,779)	(11,779)
Issuance of series E convertible preferred stock, net of issuance costs	$ 0	$ 0	0	0	0
Issuance of series E convertible preferred stock, net of issuance costs (in shares)	0	0
Common stock issued upon exercise of stock options	$ 0	$ 0	999	0	999
Common stock issued upon exercise of stock options (in shares)	581,237	0
Stock-based compensation expense	$ 0	$ 0	457	0	457
Balance at Mar. 31, 2021	$ 1	$ 0	13,973	(184,022)	(170,048)
Balance (in shares) at Mar. 31, 2021	5,959,524	0
Balance at Dec. 31, 2020					$ 195,814
Balance (in shares) at Dec. 31, 2020					90,789,268
Balance at Sep. 30, 2021					$ 0
Balance (in shares) at Sep. 30, 2021					0
Balance at Dec. 31, 2020	$ 1	$ 0	12,517	(172,243)	$ (159,725)
Balance (in shares) at Dec. 31, 2020	5,378,287	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss					(65,567)
Balance at Sep. 30, 2021	$ 12	$ 2	731,711	(237,810)	493,915
Balance (in shares) at Sep. 30, 2021	116,717,990	19,937,500
Balance at Mar. 31, 2021					$ 195,810
Balance (in shares) at Mar. 31, 2021					90,789,268
Increase (Decrease) in Temporary Equity [Roll Forward]
Conversion of the convertible preferred stock into Class A and B common stock					$ (195,810)
Conversion of the convertible preferred stock into Class A and B common stock (in shares)					(90,789,268)
Balance at Jun. 30, 2021					$ 0
Balance (in shares) at Jun. 30, 2021					0
Balance at Mar. 31, 2021	$ 1	$ 0	13,973	(184,022)	$ (170,048)
Balance (in shares) at Mar. 31, 2021	5,959,524	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ 0	$ 0	0	(35,697)	(35,697)
Common stock issued upon exercise of stock options	$ 0	$ 0	2,712	0	2,712
Common stock issued upon exercise of stock options (in shares)	1,327,823	0
Conversion of the convertible preferred stock into common stock	$ 5	$ 2	195,803	0	195,810
Conversion of the convertible preferred stock into common stock (in shares)	52,466,941	19,937,500
Net equity infusion from the Business Combination	$ 6	$ 0	501,166	0	501,172
Net equity infusion from the Business Combination (in shares)	56,708,872	0
Stock-based compensation expense	$ 0	$ 0	9,987	0	9,987
Balance at Jun. 30, 2021	$ 12	$ 2	723,641	(219,719)	503,936
Balance (in shares) at Jun. 30, 2021	116,463,160	19,937,500
Balance at Sep. 30, 2021					$ 0
Balance (in shares) at Sep. 30, 2021					0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ 0	$ 0	0	(18,091)	$ (18,091)
Common stock issued upon exercise of stock options	$ 0	$ 0	676	0	676
Common stock issued upon exercise of stock options (in shares)	254,830	0
Net equity infusion from the Business Combination	$ 0	$ 0	(2)	0	(2)
Net equity infusion from the Business Combination (in shares)	0	0
Stock-based compensation expense	$ 0	$ 0	7,396	0	7,396
Balance at Sep. 30, 2021	$ 12	$ 2	$ 731,711	$ (237,810)	$ 493,915
Balance (in shares) at Sep. 30, 2021	116,717,990	19,937,500

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Cash flows from operating activities:
Net loss	$ (18,091)	$ (11,779)	$ (8,557)	$ (10,314)	$ (65,567)	$ (27,068)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	264		222		712	676
Unrealized losses of marketable securities					634	0
Loss on disposal of fixed assets					0	2
Change in fair value of warrant liabilities					(3,442)	0
Stock-based compensation expense					17,840	1,601
Changes in operating assets and liabilities:
Prepaid expenses and other current assets					(4,049)	(155)
Other assets					(117)	0
Other assets - related party					738	228
Accounts payable					1,268	411
Accrued expenses and other current liabilities					2,627	1
Other long-term liabilities					239	0
Net cash used in operating activities					(49,117)	(24,304)
Cash flows from investing activities:
Purchases of property and equipment					(2,354)	(432)
Purchases of marketable securities					(438,736)	0
Net cash used in investing activities					(441,090)	(432)
Cash flows from financing activities:
Proceeds from exercise of stock options					4,387	42
Proceeds from issuance of Series E convertible preferred stock					0	10,310
Net proceeds from equity infusion from the Business Combination					512,794	0
Proceeds from issuance of notes payable					0	1,749
Payment of notes payable					(1,749)	0
Stock issuance costs for Series E convertible preferred stock					(4)	(34)
Principal payments under capital lease obligations					(28)	(28)
Net cash provided by financing activities					515,400	12,039
Net increase (decrease) in cash and cash equivalents					25,193	(12,697)
Cash and cash equivalents at beginning of period		$ 36,910		$ 32,930	36,910	32,930	$ 32,930
Cash and cash equivalents at end of period	$ 62,103		$ 20,233		62,103	20,233	$ 36,910
Supplemental disclosure of cash flow information:
Cash received from exchange of research and development tax credits					377	0
Supplemental disclosure of noncash information:
Noncash acquisition of property and equipment					599	18
Forgiveness of related party promissory notes					150	20
Noncash equity related transaction costs from the Business Combination					6	0
Noncash equity related warrants from the Business Combination					11,618	0
Conversion of the convertible preferred stock into Class A and Class B common stock					$ 195,810	$ 0

ORGANIZATION AND DESCRIPTION OF

ORGANIZATION AND DESCRIPTION OF BUSINESS	9 Months Ended
	Sep. 30, 2021
ORGANIZATION AND DESCRIPTION OF BUSINESS [Abstract]
ORGANIZATION AND DESCRIPTION OF BUSINESS	1. ORGANIZATION AND DESCRIPTION OF BUSINESS Quantum-Si Incorporated (“Quantum-Si”, the “Company”, “we”, “us” and “our”), formerly known as HighCape Capital Acquisition Corp. (“HighCape”), was incorporated as a Delaware corporation on June 10, 2020. The Company’s legal name became Quantum-Si Incorporated in connection with the closing of the Business Combination on June 10, 2021 (the “Closing”), as defined and described in Note 3 “Business Combination”. In connection with the Closing, Quantum-Si Incorporated, a Delaware corporation (“Legacy Quantum-Si”), merged with and into a wholly-owned subsidiary of HighCape, became a wholly-owned subsidiary of the Company, and changed its name to Q-SI Operations Inc. The prior period financial information represents the financial results and condition of Legacy Quantum-Si. The Company is an innovative life sciences company with the mission of transforming single molecule analysis and democratizing its use by providing researchers and clinicians access to the proteome, the set of proteins expressed within a cell. The Company has developed a proprietary universal single molecule detection platform that the Company is first applying to proteomics to enable Next Generation Protein Sequencing (“NGPS”) , the ability to sequence proteins in a massively parallel fashion (rather than sequentially, one at a time), and can be used for the study of nucleic acids Although the Company has incurred recurring losses in each year since inception, the Company expects its cash and cash equivalents, and marketable securities will be able to fund its operations for at least the next twelve months.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	9 Months Ended
	Sep. 30, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation and Principles of Consolidation The accompanying condensed consolidated financial statements include the accounts of the Company and have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and pursuant to the accounting disclosure rules and regulations of the Securities and Exchange Commission (the “SEC”) regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. These condensed consolidated financial statements should be read in conjunction with the financial statements and notes included in the Legacy Quantum-Si audited financial statements as of and for the years ended December 31, 2020 and 2019. The condensed consolidated balance sheet as of December 31, 2020 included herein was derived from the audited financial statements as of that date, but does not include all disclosures, including certain notes required by U.S. GAAP, on an annual reporting basis. In the opinion of management, the accompanying condensed consolidated financial statements reflect all normal recurring adjustments necessary to present fairly the financial position, results of operations, and cash flows for the interim periods. The results for the three and nine months ended September 30, 2021 are not necessarily indicative of the results to be expected for any subsequent quarter, the year ending December 31, 2021, or any other period. Except as described elsewhere in this Note 2 under the heading “Recently Issued Accounting Pronouncements” and Note 3 “Business Combination”, there have been no material changes to the Company’s significant accounting policies as described in the Legacy Quantum-Si audited financial statements as of and for the years ended December 31, 2020 and 2019. COVID-19 Outbreak The outbreak of the novel coronavirus (“COVID-19”), which was declared a pandemic by the World Health Organization on March 11, 2020 and declared a National Emergency by the President of the United States on March 13, 2020, has led to adverse impacts on the U.S. and global economies and created uncertainty regarding potential impacts on the Company’s operating results, financial condition and cash flows. The COVID-19 pandemic had, and is expected to continue to have, an adverse impact on the Company’s operations, particularly as a result of preventive and precautionary measures that the Company, other businesses, and governments are taking. Governmental mandates related to COVID-19 or other infectious diseases, or public health crises, have impacted, and the Company expects them to continue to impact, its personnel and personnel at third-party manufacturing facilities in the United States and other countries, and the availability or cost of materials, which would disrupt or delay the Company’s receipt of instruments, components and supplies from the third parties the Company relies on to, among other things, produce its products currently under development. The COVID-19 pandemic has also had an adverse effect on the Company’s ability to attract, recruit, interview and hire at the pace the Company would typically expect to support its rapidly expanding operations. To the extent that any governmental authority imposes additional regulatory requirements or changes existing laws, regulations, and policies that apply to the Company’s business and operations, such as additional workplace safety measures, the Company’s product development plans may be delayed, and the Company may incur further costs in bringing its business and operations into compliance with changing or new laws, regulations, and policies. The full extent to which the COVID-19 pandemic will directly or indirectly impact the Company’s business, results of operations and financial condition, including expenses and research and development costs, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19 and the actions taken to contain or treat COVID-19, as well as the economic impacts. The estimates of the impact on the Company’s business may change based on new information that may emerge concerning COVID-19 and the actions to contain it or address its impact and the economic impact on local, regional, national and international markets. While the Company is unable to predict the full impact that the COVID-19 pandemic will have on the Company’s future results of operations, liquidity and financial condition due to numerous uncertainties, including the duration of the pandemic, and the actions that may be taken by government authorities across the United States, it is not expected to result in any significant changes in costs going forward. The Company has not incurred any significant impairment losses in the carrying values of the Company’s assets as a result of the COVID-19 pandemic and is not aware of any specific related event or circumstance that would require the Company to revise its estimates reflected in its condensed consolidated financial statements. Concentration of Credit Risk Financial instruments that potentially subject the Company to concentration of credit risk consist principally of cash and cash equivalents and marketable securities. At September 30, 2021 and December 31, 2020, substantially all of the Company’s cash and cash equivalents and marketable securities were invested in mutual funds at one financial institution. The Company also maintains balances in various operating accounts above federally insured limits. The Company has not experienced any losses on such accounts and does not believe it is exposed to any significant credit risk on cash and cash equivalents and marketable securities. Use of Estimates The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires the Company to make estimates and assumptions about future events that affect the amounts reported in its condensed consolidated financial statements and accompanying notes. Future events and their effects cannot be determined with certainty. On an ongoing basis, management evaluates these estimates and assumptions. Significant estimates and assumptions included: • valuation allowances with respect to deferred tax assets; • valuation of warrant liabilities; and • assumptions underlying the fair value used in the calculation of the stock-based compensation. The Company bases these estimates on historical and anticipated results and trends and on various other assumptions that the Company believes are reasonable under the circumstances, including assumptions as to future events. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates, and any such differences may be material to the Company’s condensed consolidated financial statements. Investments in Marketable Securities The Company’s investments in marketable securities are ownership interests in fixed income mutual funds. The securities are stated at fair value, as determined by quoted market prices. As the securities have readily determinable fair value, unrealized gains and losses are reported as other (expense), net on the condensed consolidated statements of operations and comprehensive loss. Subsequent gains or losses realized upon redemption or sale of these securities are also recorded as other (expense), net on the condensed consolidated statements of operations and comprehensive loss. The Company considers all of its investments in marketable securities as available for use in current operations and therefore classifies these securities within current assets on the condensed consolidated balance sheets. For the three and nine months ended September 30, 2021, the Company recognized $634 of unrealized losses that relate to securities still held as of September 30, 2021. Impairment of Long-Lived Assets The Company reviews its long-lived assets for impairment at least annually or when the Company determines a triggering event has occurred. When a triggering event has occurred, each impairment test is based on a comparison of the future expected undiscounted cash flow to the recorded value of the asset. If the recorded value of the asset is less than the undiscounted cash flow, the asset is written down to its estimated fair value. No impairments were recorded for the three and nine months ended September 30, 2021 and 2020. Warrant Liabilities The Company’s outstanding warrants include publicly-traded warrants (the “Public Warrants”) which were issued as one-third Derivatives and Hedging-Contracts in Entity’s Own Equity Recently Issued Accounting Pronouncements Accounting pronouncements issued but not yet adopted In February 2016, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) 2016-02, Leases (Topic 842) , Revenue from Contracts with Customers (Topic 606) and Leases (Topic 842): Effective Dates for Certain Entities, In August 2018, the FASB issued ASU 2018-15, Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that Is a Service Contract In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes In August 2020, the FASB issued ASU 2020-06, Debt-Debt with Conversion and Other Options (Subtopic 470-20) Derivatives and Hedging-Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity

BUSINESS COMBINATION

BUSINESS COMBINATION	9 Months Ended
	Sep. 30, 2021
BUSINESS COMBINATION [Abstract]
BUSINESS COMBINATION	3. BUSINESS COMBINATION On June 10, 2021, Quantum-Si Incorporated, a Delaware corporation (“Legacy Quantum-Si”), consummated the previously announced business combination (the “Business Combination”) with HighCape in which Legacy Quantum-Si merged with a wholly-owned subsidiary of HighCape (the “Merger”) and survived the Business Combination as a wholly-owned subsidiary of the Company. In connection with the Business Combination, the Company changed its name to Quantum-Si Incorporated and Legacy Quantum-Si changed its name to Q-SI Operations Inc. The Business Combination is accounted for as a reverse recapitalization in accordance with U.S. GAAP primarily due to the fact that Legacy Quantum-Si stockholders continued to control the Company following the Closing of the Business Combination. Under this method of accounting, HighCape is treated as the “acquired” company for accounting purposes and the Business Combination is treated as the equivalent of Legacy Quantum-Si issuing stock for the net assets of HighCape, accompanied by a recapitalization. The net assets of HighCape are stated at historical cost, with no goodwill or other intangible assets recorded. Reported shares and earnings per share available to holders of the Company’s capital stock and equity awards prior to the Business Combination have been retroactively restated reflecting the exchange ratio of 0.7975 (the “Exchange Ratio”) established pursuant to the Business Combination Agreement dated as of February 18, 2021 (the “Business Combination Agreement”). Pursuant to the Business Combination Agreement, at the effective time of the Merger (the “Effective Time”): • • • • The Exchange Ratio was calculated based on the quotient resulting by dividing (i) the quotient of (x) $810,000 plus the excess of Legacy Quantum-Si cash over Legacy Quantum-Si debt as of immediately prior to the Effective Time plus the excess of certain HighCape expenses in connection with the Business Combination over $8,025 divided by (y) the number of issued and outstanding shares of Legacy Quantum-Si as of immediately prior to the Effective Time plus the number of issued vested Legacy Quantum-Si options at such time (where such number of vested options is calculated on net basis), by (ii) $10.00. On June 10, 2021, HighCape filed the Second Amended and Restated Certificate of Incorporation (the “Restated Certificate”) with the Secretary of State of the State of Delaware, which became effective simultaneously with the Effective Time. As a consequence of filing the Restated Certificate, the Company adopted a dual class structure, comprised of the Company’s Class A common stock, which is entitled to one vote per share, and the Company’s Class B common stock, which is entitled to 20 votes per share. The Company’s Class B common stock has the same economic terms as the Company’s Class A common stock, but is subject to a “sunset” provision if Jonathan M. Rothberg, Ph.D., the founder of Legacy Quantum-Si and Executive Chairman of the Company (“Dr. Rothberg”), and other permitted holders of the Company’s Class B common stock collectively cease to beneficially own at least twenty percent (20%) of the number of shares of the Company’s Class B common stock (as such number of shares is equitably adjusted in respect of any reclassification, stock dividend, subdivision, combination or recapitalization of the Company’s Class B common stock) collectively held by Dr. Rothberg and permitted transferees of the Company’s Class B common stock as of the Effective Time. Concurrently with the execution of the Business Combination Agreement, HighCape entered into subscription agreements (the “PIPE Investor Subscription Agreements”) with certain institutional investors and accredited investors (the “PIPE Investors”), pursuant to which the PIPE Investors purchased, immediately prior to the Closing, an aggregate of 42,500,000 shares of HighCape Class A common stock at a purchase price of $10.00 per share (the “PIPE Financing”). In addition, concurrently with the execution of the Business Combination Agreement, HighCape entered into subscription agreements (the “Subscription Agreements”), with certain affiliates of Foresite Capital Management, LLC (the “Foresite Funds”), pursuant to which the Foresite Funds purchased immediately prior to the Closing, an aggregate of 696,250 shares of HighCape Class A common stock at a purchase price of $0.001 per share for aggregate gross proceeds of $1 after a corresponding number of shares of HighCape Class B common stock was irrevocably forfeited by HighCape’s Sponsor to HighCape for no consideration and automatically cancelled. The total number of shares of the Company’s Class A common stock outstanding immediately following the Closing was 116,463,160, comprising: • • 42,500,000 shares of the Company’s Class A common stock issued in connection with the Closing to the PIPE Investors pursuant to the PIPE Financing, • • • • The total number of shares of the Company’s Class B common stock outstanding immediately following the Closing was 19,937,500 shares. Immediately following the Closing, Dr. Rothberg held approximately 80.4% of the combined voting power of the Company. Accordingly, Dr. Rothberg and his permitted transferees control the Company and the Company is a controlled company within the meaning of the Nasdaq listing rules. The most significant change in the post-combination Company’s reported financial position and results was an increase in cash of $540,276 consisting of $425,001 from the PIPE investors and $115,275 from HighCape. The increase in cash was offset by transaction costs of $17,824, payment of the Paycheck Protection Program (“PPP”) loan of $1,764 including interest, payments to redeeming Company shareholders of $5,712, and payment of $3,800 to a third-party service provider, resulting in proceeds of $511,176 on the date of the Closing of the Business Combination on June 10, 2021. In addition, the post-combination balance sheet increased by the warrant liabilities of $11,618 and other insignificant assets and liabilities. Additional transaction costs were incurred prior to the Business Combination not settled on the date of Closing. Transaction costs of $7,383 were expensed during the nine months ended September 30, 2021 in the condensed consolidated statements of operations and comprehensive loss. On the date of Closing, the proceeds of $540,276 were offset against the warrant liabilities of payments to redeeming Company shareholders of and other liabilities and related transaction costs of , which resulted in an equity infusion from the Business Combination of in the condensed consolidated statements of changes in convertible preferred stock and stockholders’ equity (deficit) for the nine months ended September 30, 2021.

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	9 Months Ended
	Sep. 30, 2021
FAIR VALUE OF FINANCIAL INSTRUMENTS [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS	4. FAIR VALUE OF FINANCIAL INSTRUMENTS Fair value estimates of financial instruments are made at a specific point in time, based on relevant information about financial markets and specific financial instruments. As these estimates are subjective in nature, involving uncertainties and matters of significant judgment, they cannot be determined with precision. Changes in assumptions can significantly affect estimated fair value. The Company measures fair value as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the reporting date. The Company utilizes a three-tier hierarchy, which prioritizes the inputs used in the valuation methodologies in measuring fair value: • Level 1 • Level 2 • Level 3 The carrying value of cash and cash equivalents, notes receivable, accounts payable and accrued expenses and other current liabilities approximates their fair values due to the short-term or on demand nature of these instruments. There were no transfers between fair value measurement levels during the three and nine months ended September 30, 2021. The Company accounted for the warrants as liabilities in accordance with ASC 815-40 and are presented within warrant liabilities on the condensed consolidated balance sheets. The warrant liabilities are measured at fair value at inception and on a recurring basis, with changes in fair value presented within change in fair value of warrant liabilities in the condensed consolidated statements of operations and comprehensive loss. Our Public Warrants and Private Warrants were carried at fair value as of September 30, 2021. The Public Warrants were valued using Level 1 inputs as they are traded in an active market. The Private Warrants were valued using a binomial lattice model, which results in a Level 3 fair value measurement. The primary unobservable input utilized in determining the fair value of the Private Warrants was the expected volatility of the Company’s Class A common stock. The expected volatility was based on consideration of the implied volatility from the Company’s own public warrant pricing and on the historical volatility observed at guideline public companies. As of September 30, 2021, the significant assumptions used in preparing the binomial lattice model for valuing the Private Warrants liability include (i) volatility of 52.3%, (ii) risk-free interest rate of 0.91%, (iii) strike price ($11.50), (iv) fair value of common stock ($8.34), and (v) expected life of 4.7 years. Mutual funds were valued using quoted market prices and accordingly were classified as Level 1. The following table summarizes the Company’s assets and liabilities that are measured at fair value on a recurring basis, by level, within the fair value hierarchy as of September 30, 2021: Fair Value Measurement Level Total Level 1 Level 2 Level 3 September 30, 2021: Assets: Mutual funds - Cash and cash equivalents $ 59,896 $ 59,896 $ - $ - Mutual funds - Marketable securities 438,102 438,102 - - Total assets at fair value on a recurring basis $ 497,998 $ 497,998 $ - $ - Liabilities: Public Warrants $ 7,782 $ 7,782 $ - $ - Private Warrants 394 - - 394 Total liabilities at fair value on a recurring basis $ 8,176 $ 7,782 $ - $ 394 The Company had $36,040 of money market funds included in cash and cash equivalents as of December 31, 2020. These assets were valued using quoted market prices and accordingly were classified as Level 1. The fair value of the notes payable using Level 2 inputs was deemed to approximate the carrying value as of December 31, 2020. There were no transfers between fair value measurement levels during the year ended December 31, 2020.

PROPERTY AND EQUIPMENT, NET

PROPERTY AND EQUIPMENT, NET	9 Months Ended
	Sep. 30, 2021
PROPERTY AND EQUIPMENT, NET [Abstract]
PROPERTY AND EQUIPMENT, NET	5. PROPERTY AND EQUIPMENT, NET Property and equipment, net, are recorded at historical cost and consist of the following: September 30, December 31, Laboratory equipment $ 5,885 $ 4,245 Computer equipment 996 765 Software 156 136 Furniture and fixtures 47 47 Leasehold improvements 22 - Construction in process 1,045 35 8,151 5,228 Less: Accumulated depreciation (3,944 ) (3,232 ) Property and equipment, net $ 4,207 $ 1,996 Depreciation expense amounted to $264 and $222 for the three months ended September 30, 2021 and 2020, respectively, and $712 and $676 for the nine months ended September 30, 2021 and 2020, respectively.

ACCRUED EXPENSES AND OTHER CURR

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES	9 Months Ended
	Sep. 30, 2021
ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES [Abstract]
ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES	6. ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES Accrued expenses and other current liabilities consist of the following: September 30, December 31, Employee compensation $ 1,703 $ 511 Contracted services 1,114 399 Legal fees 1,147 447 Other 60 68 Total accrued expenses and other current liabilities $ 4,024 $ 1,425

NOTES PAYABLE

NOTES PAYABLE	9 Months Ended
	Sep. 30, 2021
NOTES PAYABLE [Abstract]
NOTES PAYABLE	7. NOTES PAYABLE In August 2020, the Company received loan proceeds of $1,749 under the PPP. The Company used the loan proceeds for eligible purposes, including payroll, benefits, rent and utilities, and maintains its payroll levels. The Company accounted for the loan as debt. In connection with the Closing of the Business Combination as discussed in Note 3 “Business Combination”, the Company repaid the loan in full in June 2021. The Company recognized an insignificant amount of interest expense in the condensed consolidated statements of operations and comprehensive loss related to the loan.

CONVERTIBLE PREFERRED STOCK

CONVERTIBLE PREFERRED STOCK	9 Months Ended
	Sep. 30, 2021
CONVERTIBLE PREFERRED STOCK [Abstract]
CONVERTIBLE PREFERRED STOCK	8. CONVERTIBLE PREFERRED STOCK The Company had issued five series of convertible preferred stock, Series A through Series E (the “Convertible Preferred Stock”). The following table summarizes the authorized, issued and outstanding Convertible Preferred Stock of the Company immediately prior to the Business Combination and as of December 31, 2020: Class Year of Class Issuance Issuance Price per Share Shares Authorized Shares Issued and Outstanding Total Proceeds or Exchange Value Issuance Costs Net Carrying Value Initial Liquidation Price per Share Series A 2013 $ 0.04 25,000,000 25,000,000 $ 1,000 $ - $ 1,000 $ 0.80 Series B 2015 0.80 31,250,000 31,250,000 25,000 - 25,000 0.80 Series C 2015 2016 4.61 8,164,323 8,164,323 37,638 328 37,310 4.61 Series D 2017 4.71 12,738,853 12,738,853 60,000 414 59,586 4.71 Series E 2018 2020 5.36 14,925,373 13,636,092 73,089 171 72,918 5.36 92,078,549 90,789,268 Prior to the Closing of the Business Combination, there were no significant changes to the terms of the Convertible Preferred Stock as compared to December 31, 2020. Upon the Closing of the Business Combination, the Convertible Preferred Stock converted into Class A and Class B common stock based on the Business Combination’s Exchange Ratio of 0.7975 of the Company’s shares for each Legacy Quantum-Si share. The Company recorded the conversion at the carrying value of the Convertible Preferred Stock at the time of the Closing. There are no shares of Convertible Preferred Stock outstanding as of September 30, 2021.

EQUITY INCENTIVE PLAN

EQUITY INCENTIVE PLAN	9 Months Ended
	Sep. 30, 2021
EQUITY INCENTIVE PLAN [Abstract]
EQUITY INCENTIVE PLAN	9. EQUITY INCENTIVE PLAN The Company’s 2013 Employee, Director and Consultant Equity Incentive Plan, as amended on March 12, 2021 (the “2013 Plan”), was originally adopted by its Board of Directors and stockholders in September 2013. In connection with the Closing of the Business Combination, the Company adjusted the equity awards as described in Note 3 “Business Combination”. The adjustments to the awards did not result in incremental expense as the equitable adjustments were made pursuant to a preexisting nondiscretionary antidilution provision in the 2013 Plan, and the fair-value, vesting conditions, and classification are the same immediately before and after the modification. In connection with the Business Combination, HighCape’s stockholders approved and adopted the Quantum-Si Incorporated 2021 Equity Incentive Plan (the “2021 Plan”). The 2021 Plan provides for grants of stock options, stock appreciation rights, restricted stock, restricted stock units, and other stock or cash-based awards. Directors, officers and other employees of the Company and its subsidiaries, as well as others performing consulting or advisory services for the Company, are eligible for grants under the 2021 Plan. Stock option activity During the nine months ended September 30, 2021, the Company granted 3,104,585 option awards subject to service and/or performance conditions. The service condition requires the participant’s continued employment with the Company through the applicable vesting date, and the performance condition requires the consummation of a contemplated business combination defined in the option award agreement. For options with performance conditions, stock-based compensation expense is only recognized if the performance conditions become probable to be satisfied. As the performance condition is a business combination, the performance condition would only become probable once a business combination was consummated. Accordingly, the Company recorded stock-based compensation expense of $2,381 for the nine months ended September 30, 2021 including $1,343 related to these option awards during the six months ended June 30, 2021, as the Business Combination was consummated during this time period. The stock-based compensation expense for stock options for the three and nine months ended September 30, 2021 was $1,556 and $4,608, respectively. A summary of the stock option activity under the 2013 Plan and the 2021 Plan is presented in the table below: Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value Outstanding at December 31, 2020 7,369,541 $ 2.37 6.77 $ 4,094 Granted 3,104,585 9.07 Exercised (2,163,932 ) 2.03 Forfeited (184,017 ) 8.64 Outstanding at September 30, 2021 8,126,177 $ 4.88 7.59 $ 30,222 Options exercisable at September 30, 2021 4,371,817 2.61 6.21 $ 25,100 Vested and expected to vest at September 30, 2021 7,805,361 $ 4.78 7.53 $ 29,784 Restricted stock unit activity During the nine months ended September 30, 2021, the Company granted 4,861,315 restricted stock unit (“RSU”) awards subject to service, performance and/or market conditions. The RSU awards include 1,703,460 and 170,346 RSU awards to the Company’s Chief Executive Officer and General Counsel, respectively, subject to service and performance conditions, 1,800,000 RSU awards to the Executive Chairman of the Company and two members of the board of directors subject to service and/or performance conditions, and 453,777 RSU awards to the Company’s Chief Executive Officer subject to service, market and performance conditions. The service condition requires the participant’s continued employment with the Company through the applicable vesting date, and the performance condition requires the consummation of a contemplated business combination or financing transaction defined in the award agreement. The market condition requires that the Company’s Class A common stock subsequent to a business combination trades above a specified level for a defined period of time, or that a subsequent financing transaction meets defined pricing thresholds and that the Company’s common stock subsequent to a business combination trades above a specified level for a defined period of time. For RSU awards with performance conditions, stock-based compensation expense is only recognized if the performance conditions become probable to be satisfied. As the performance condition is a business combination or financing transaction, the performance condition would only become probable once a business combination or financing transaction was consummated. Accordingly, the Company recorded stock-based compensation expense of $13,089 for the nine months ended September 30, 2021 including $7,393 related to these RSU awards during the six months ended June 30, 2021, as the Business Combination was consummated during this time period. The stock-based compensation expense for RSU awards for the three and nine months ended September 30,2021 was $5,840 and $13,232, respectively. A summary of the RSU activity under the 2013 Plan and the 2021 Plan is presented in the table below: Number of Shares Underlying RSUs Weighted Average Grant- Date Fair Value Outstanding non-vested RSUs at December 31, 2020 - $ - Granted 4,861,315 8.03 Repurchased - - Restrictions lapsed - - Outstanding non-vested RSUs at September 30, 2021 4,861,315 $ 8.03 The Company’s stock-based compensation expense is allocated to the following operating expense categories as follows: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 Research and development $ 1,520 $ 355 $ 4,343 $ 1,217 General and administrative 5,626 64 12,918 160 Sales and marketing 250 74 579 224 Total stock-based compensation expense $ 7,396 $ 493 $ 17,840 $ 1,601

NET LOSS PER SHARE

NET LOSS PER SHARE	9 Months Ended
	Sep. 30, 2021
NET LOSS PER SHARE [Abstract]
NET LOSS PER SHARE	10 . NET LOSS PER SHARE Basic net loss per share is computed by dividing the net loss by the weighted-average number of shares of common stock of the Company outstanding during the period. Diluted net loss per share is computed by giving effect to all common share equivalents of the Company, including outstanding Convertible Preferred Stock and stock options, to the extent dilutive. Basic and diluted net loss per share was the same for each period presented as the inclusion of all common share equivalents would have been anti-dilutive. The following table presents the calculation of basic and diluted net loss per share for the Company’s common stock: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 Numerator Net loss $ (18,091 ) $ (8,557 ) $ (65,567 ) $ (27,068 ) Numerator for basic and diluted EPS - loss attributable to common stockholders $ (18,091 ) $ (8,557 ) $ (65,567 ) $ (27,068 ) Denominator Common stock 136,456,848 5,360,497 60,104,891 5,350,771 Denominator for basic and diluted EPS - weighted-average common stock 136,456,848 5,360,497 60,104,891 5,350,771 Basic and diluted net loss per share $ (0.13 ) $ (1.60 ) $ (1.09 ) $ (5.06 ) Since the Company was in a net loss position for all periods presented, the basic net loss per shares calculation excludes preferred stock as it does not participate in net losses of the Company. Additionally, net loss per share attributable to Class A and Class B common stockholders was the same on a basic and diluted basis, as the inclusion of all potential common equivalent shares outstanding would have been anti-dilutive. Anti-dilutive common equivalent shares were as follows: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 Outstanding options to purchase common stock 8,126,177 7,978,697 8,126,177 7,978,697 Outstanding restricted stock units 4,861,315 - 4,861,315 - Outstanding warrants 3,968,319 - 3,968,319 - Outstanding convertible preferred stock (Series A through E) - 68,684,758 - 68,684,758 16,955,811 76,663,455 16,955,811 76,663,455 During the three months ended September 30, 2021, the Company identified a misstatement in the basic and diluted net loss per share calculation including the weighted-average common stock for the three and six months ended June 30, 2021. The Company has evaluated this correction in accordance with ASC 250-10-S99, Securities and Exchange Commission “SEC” Materials (formerly SEC Staff Accounting Bulletin 99, Materiality ) and concluded that the correction was not material. The Company plans on adjusting the basic and diluted net loss per share calculation including the weighted-average common stock in its future filings such as the Form 10-K for the year ending December 31, 2021 and in Form 10-Q for the three and six months ending June 30, 2022. The adjustments to the Company’s previously issued condensed consolidated statements of operations and comprehensive loss and Note 10 to our Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2021 are as follows: Three months ended June 30, 2021 Six months ended June 30, 2021 As Reported As Revised As Reported As Revised Denominator Common stock 11,696,084 36,890,502 8,629,355 21,296,162 Denominator for basic and diluted EPS - weighted-average common stock 11,696,084 36,890,502 8,629,355 21,296,162 Basic and diluted net loss per share $ (3.05 ) $ (0.97 ) $ (5.50 ) $ (2.23 )

WARRANT LIABILITIES

WARRANT LIABILITIES	9 Months Ended
	Sep. 30, 2021
WARRANT LIABILITIES [Abstract]
WARRANT LIABILITIES	11. WARRANT LIABILITIES Public Warrants As of September 30, 2021, there were an aggregate of 3,833,319 outstanding Public Warrants, which entitle the holder to acquire Class A common stock. Each whole warrant entitles the registered holder to purchase one share of Class A common stock at an exercise price of $11.50 per share, subject to adjustment as discussed below, beginning on September 9, 2021. The warrants will expire on June 10, 2026 or earlier upon redemption or liquidation. Redemptions At any time while the warrants are exercisable, the Company may redeem not less than all of the outstanding Public Warrants: • • • • three If the foregoing conditions are satisfied and the Company issues a notice of redemption of the Public Warrants at $0.01 per warrant, each holder of Public Warrants will be entitled to exercise his, her or its Public Warrants prior to the scheduled redemption date. If the Company calls the Public Warrants for redemption for $0.01 as described above, the Company’s Board of Directors may elect to require any holder that wishes to exercise his, her or its Public Warrants to do so on a “cashless basis.” If the Company’s Board of Directors makes such election, all holders of Public Warrants would pay the exercise price by surrendering their warrants for that number of shares of Class A common stock equal to the quotient obtained by dividing (x) the product of the number of shares of Class A common stock underlying the warrants, multiplied by the excess of the “fair market value” ​over the exercise price of the warrants by (y) the “fair market value”. For purposes of the redemption provisions of the warrants, the “fair market value” means the average last reported sale price of the Class A common stock for the 10 trading days ending on the third trading day prior to the date on which the notice of redemption is sent to the holders of warrants. The Company evaluated the Public Warrants under ASC 815-40, in conjunction with the SEC Division of Corporation Finance’s April 12, 2021 Public Statement, Staff Statement on Accounting and Reporting Considerations for Warrants Issued by Special Purpose Acquisition Companies (“SPACs”) Private Warrants As of September 30, 2021, there were 135,000 Private Warrants outstanding. The Private Warrants are identical to the Public Warrants, except that so long as they are held by the Sponsor or any of its permitted transferees, (i) the Private Warrants and the shares of Class A common stock issuable upon the exercise of the Private Warrants were not transferable, assignable or saleable until 30 days after the completion of the Business Combination, (ii) the Private Warrants will be exercisable for cash or on a cashless basis, at the holder’s option, and (iii) the Private Warrants are not subject to the Company’s redemption option at the price of $0.01 per warrant. The Private Warrants are subject to the Company’s redemption option at the price of $0.01 per warrant, provided that the other conditions of such redemption are met, as described above. If the Private Warrants are held by a holder other than the Sponsor or any of its permitted transferees, the Private Warrants will be redeemable by the Company in all redemption scenarios applicable to the Public Warrants and exercisable by such holders on the same basis as the Public Warrants. The Company evaluated the Private Warrants under ASC 815-40, in conjunction with the SEC Statement , The fair value of warrant liabilities was $11,618 and $8,176 as of the Closing of the Business Combination and as of September 30, 2021, respectively. The Company recognized a gain of $6,975 and $3,442, respectively, as a change in fair value of warrant liabilities in the condensed consolidated statement of operations and comprehensive loss for the three and nine months ended September 30, 2021. There were no exercises or redemptions of the Public Warrants or Private Warrants during the three and nine months ended September 30, 2021.

INCOME TAXES

INCOME TAXES	9 Months Ended
	Sep. 30, 2021
INCOME TAXES [Abstract]
INCOME TAXES	12. INCOME TAXES Income taxes for the three and nine months ended September 30, 2021 and 2020 are recorded at the Company’s estimated annual effective income tax rate, subject to adjustments for discrete events, if they occur. The Company’s estimated annual effective tax rate was 0.0% for the three and nine months ended September 30, 2021 and 2020. The primary reconciling items between the federal statutory rate of 21.0% for these periods and the Company’s overall effective tax rate of 0.0% were related to the effects of deferred state income taxes, nondeductible stock-based compensation, changes in the fair value of warrant liabilities, research and development credits, and the valuation allowance recorded against the full amount of its net deferred tax assets. A valuation allowance is required when it is more likely than not that some portion or all of the Company’s deferred tax assets will not be realized. The realization of deferred tax assets depends on the generation of sufficient future taxable income during the period in which the Company’s related temporary differences become deductible. The Company has recorded a full valuation allowance against its net deferred tax assets as of September 30, 2021 and 2020 since management believes that based on the earnings history of the Company, it is more likely than not that the benefits of these assets will not be realized. As a result of the Business Combination, as well as any other equity issuances during the year, the Company is currently evaluating whether an ownership change has occurred under Section 382 of the Internal Revenue Code of 1986, as amended, and whether the Company’s ability to use its pre-change net operating loss and tax credit carryforwards will be limited in future periods. The Company expects to complete its analysis during 2022.

RELATED PARTY TRANSACTIONS

RELATED PARTY TRANSACTIONS	9 Months Ended
	Sep. 30, 2021
RELATED PARTY TRANSACTIONS [Abstract]
RELATED PARTY TRANSACTIONS	13. RELATED PARTY TRANSACTIONS The Company utilizes and subleases office and laboratory space in a building owned by a related party. The Company paid $80 and $241 for this space for the three and nine months ended September 30, 2021 and 2020, respectively. The Company utilizes and subleases other office and laboratory spaces from 4Catalyzer Corporation (“4C”), a company under common ownership. The Company paid $36 and $36 for these spaces for the three months ended September 30, 2021 and 2020, respectively, and $112 and $117 for these spaces for the nine months ended September 30, 2021 and 2020, respectively. The Company also made payments to 4C to prefund the acquisition of certain shared capital assets, reflected in Other assets - related party on the condensed consolidated balance sheets of $0 and $738 at September 30, 2021 and December 31, 2020, respectively. The Company was a party to an Amended and Restated Technology Services Agreement (the “ARTSA”), most recently amended on November 11, 2020, by and among 4C, the Company and other participant companies controlled by the Rothberg family. The Company entered into a First Addendum to the ARTSA on February 17, 2021 pursuant to which the Company agreed to terminate its participation under the ARTSA no later than immediately prior to the Effective Time of the Business Combination, resulting in the termination of the Company’s participation under the ARTSA on June 10, 2021. In connection with the termination of the Company’s participation under the ARTSA, the Company terminated its lease agreement with 4C and negotiated an arm’s length lease agreement. As a result, the Company wrote off Other assets – related party of $700 which was recorded in General and administrative in the condensed consolidated statements of operations and comprehensive loss for the nine months ended September 30, 2021. Under the ARTSA, the Company and the other participant companies had agreed to share certain non-core technologies, which means any technologies, information or equipment owned or otherwise controlled by the participant company that are not specifically related to the core business area of the participant and subject to certain restrictions on use. The ARTSA also provided for 4C to perform certain services for the Company and each other participant company such as monthly administrative, management and technical consulting services to the Company which were pre-funded approximately once per quarter. The Company incurred expenses of $203 and $396 during the three months ended September 30, 2021 and 2020, respectively, and $1,782 and $1,073 during the nine months ended September 30, 2021 and 2020, respectively. The amounts advanced and due from 4C at September 30, 2021 and December 31, 2020, related to operating expenses was $0 and $13, respectively, and are included in Prepaid expenses and other current assets on the condensed consolidated balance sheets. The ARTSA also provided for the participant companies to provide other services to each other. The Company also had transactions with other entities under common ownership, which included payments made to third parties on behalf of the Company. The amounts remaining payable at September 30, 2021 and December 31, 2020 were $170 and $28, respectively, and are included in the Accounts payable on the Company’s condensed consolidated balance sheets. In addition, the Company had transactions with these other entities under common ownership which included payments made by the Company to third parties on behalf of the other entities. The amounts remaining payable at September 30, 2021 and December 31, 2020 are in the aggregate $158 and $69, respectively, and are reflected in the Prepaid expenses and other current assets on the Company’s condensed consolidated balance sheets. All amounts were paid or received throughout the year within 30 days after the end of each month. On September 20, 2021, the Company entered into a Binders Collaboration (the “Collaboration”) with Protein Evolution, Inc. (“PEI”) to develop technology and methods in the field of nanobodies and potentially other binders to produce novel biological reagents and related data. The Collaboration is made pursuant to and governed by the Technology and Services Exchange Agreement, effective as of June 10, 2021, by and among the Company and the participants named therein, including PEI. Dr. Rothberg serves as Chairman of the Board of Directors of PEI and the Rothberg family are controlling stockholders of PEI. The Company has not made any payments under the Collaboration for the three and nine months ended September 30, 2021. The Company had promissory notes with the President and Chief Operating Officer and other Company employees in amounts totaling $0 and $150 as of September 30, 2021 and December 31, 2020, respectively. Dr. Rothberg and the Company ( “Executive Chairman Agreement”) Dr. Rothberg to the Company for the Executive Chairman Agreement as the Company’s Chairman of the Board of Directors and a member of the Nominating and Corporate Governance Committee. Quantum-Si for the services that were provided to the Company

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
	Sep. 30, 2021
COMMITMENTS AND CONTINGENCIES [Abstract]
COMMITMENTS AND CONTINGENCIES	14. COMMITMENTS AND CONTINGENCIES Commitments Capital leases: The Company acquired equipment under a capital lease-to-own agreement which commenced July 2019 and ended June 2021. The total value of the equipment acquired through capital lease arrangements was $124. Total interest expense was $0 and $1 during the three months ended September 30, 2021 and 2020, respectively, and $1 and $5 during the nine months ended September 30, 2021 and 2020, respectively. As of September 30, 2021, there was no remaining unamortized balance of the lease obligation. Operating leases: In June 2021, the Company entered into an operating lease for a facility in San Diego, California. The lease commenced in the third quarter of 2021. Minimum rental payments under operating leases are recognized on a straight-line basis over the term of the lease. The following is a schedule of future minimum rental payments under a non-cancelable operating lease with initial terms in excess of one year: Years ending December 31: Remainder of 2021 $ 264 2022 1,186 2023 1,463 2024 1,507 2025 1,552 Thereafter 3,245 Total future minimum rental payments $ 9,217 Licenses related to certain intellectual property: The Company licenses certain intellectual property, some of which may be utilized in its future product offering. To preserve the right to use such intellectual property, the Company is required to make annual minimum fixed payments totaling $220. Once the Company commercializes its product and begins to generate revenues, there will be royalties payable by the Company based on the current anticipated utilization. Other commitments: The Company sponsors a 401(k) defined contribution plan covering all eligible U.S. employees. Contributions to the 401(k) plan are discretionary. The Company did not make any matching contributions to the 401(k) plan for the three and nine months ended September 30, 2021 and 2020. Contingencies The Company is subject to claims in the ordinary course of business; however, the Company is not currently a party to any pending or threatened litigation, the outcome of which would be expected to have a material adverse effect on its financial condition or the results of its operations. The Company accrues for contingent liabilities to the extent that the liability is probable and estimable. The Company enters into agreements that contain indemnification provisions with other parties in the ordinary course of business, including business partners, investors, contractors, and the Company’s officers, directors and certain employees. The Company has agreed to indemnify and defend the indemnified party claims and related losses suffered or incurred by the indemnified party from actual or threatened third-party claims because of the Company’s activities or non-compliance with certain representations and warranties made by the Company. It is not possible to determine the maximum potential loss under these indemnification provisions due to the Company’s limited history of prior indemnification claims and the unique facts and circumstances involved in any particular case. To date, losses recorded in the Company’s condensed consolidated statements of operations and comprehensive loss in connection with the indemnification provisions have not been material. On March 29, 2021, the Company entered into an agreement with a third-party service provider pursuant to which the Company paid $3,800, which is recorded in General and administrative in the condensed consolidated statements of operations and comprehensive loss for the nine months ended September 30, 2021, in connection with the Closing of the Business Combination as discussed in Note 3 “Business Combination.”

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	9 Months Ended
	Sep. 30, 2021
SUBSEQUENT EVENTS [Abstract]
SUBSEQUENT EVENTS	15. SUBSEQUENT EVENTS On November 5, 2021, the Company acquired Majelac Technologies LLC (“Majelac”), a privately-owned company providing semiconductor packaging and integrated circuit assembly services located in Pennsylvania. The Company acquired Majelac for an aggregate purchase price equal to $ 5,000 132 595,562 800

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
	Sep. 30, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The accompanying condensed consolidated financial statements include the accounts of the Company and have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and pursuant to the accounting disclosure rules and regulations of the Securities and Exchange Commission (the “SEC”) regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. These condensed consolidated financial statements should be read in conjunction with the financial statements and notes included in the Legacy Quantum-Si audited financial statements as of and for the years ended December 31, 2020 and 2019. The condensed consolidated balance sheet as of December 31, 2020 included herein was derived from the audited financial statements as of that date, but does not include all disclosures, including certain notes required by U.S. GAAP, on an annual reporting basis. In the opinion of management, the accompanying condensed consolidated financial statements reflect all normal recurring adjustments necessary to present fairly the financial position, results of operations, and cash flows for the interim periods. The results for the three and nine months ended September 30, 2021 are not necessarily indicative of the results to be expected for any subsequent quarter, the year ending December 31, 2021, or any other period. Except as described elsewhere in this Note 2 under the heading “Recently Issued Accounting Pronouncements” and Note 3 “Business Combination”, there have been no material changes to the Company’s significant accounting policies as described in the Legacy Quantum-Si audited financial statements as of and for the years ended December 31, 2020 and 2019.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to concentration of credit risk consist principally of cash and cash equivalents and marketable securities. At September 30, 2021 and December 31, 2020, substantially all of the Company’s cash and cash equivalents and marketable securities were invested in mutual funds at one financial institution. The Company also maintains balances in various operating accounts above federally insured limits. The Company has not experienced any losses on such accounts and does not believe it is exposed to any significant credit risk on cash and cash equivalents and marketable securities.
Use of Estimates	Use of Estimates The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires the Company to make estimates and assumptions about future events that affect the amounts reported in its condensed consolidated financial statements and accompanying notes. Future events and their effects cannot be determined with certainty. On an ongoing basis, management evaluates these estimates and assumptions. Significant estimates and assumptions included: • valuation allowances with respect to deferred tax assets; • valuation of warrant liabilities; and • assumptions underlying the fair value used in the calculation of the stock-based compensation. The Company bases these estimates on historical and anticipated results and trends and on various other assumptions that the Company believes are reasonable under the circumstances, including assumptions as to future events. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates, and any such differences may be material to the Company’s condensed consolidated financial statements.
Investments in Marketable Securities	Investments in Marketable Securities The Company’s investments in marketable securities are ownership interests in fixed income mutual funds. The securities are stated at fair value, as determined by quoted market prices. As the securities have readily determinable fair value, unrealized gains and losses are reported as other (expense), net on the condensed consolidated statements of operations and comprehensive loss. Subsequent gains or losses realized upon redemption or sale of these securities are also recorded as other (expense), net on the condensed consolidated statements of operations and comprehensive loss. The Company considers all of its investments in marketable securities as available for use in current operations and therefore classifies these securities within current assets on the condensed consolidated balance sheets. For the three and nine months ended September 30, 2021, the Company recognized $634 of unrealized losses that relate to securities still held as of September 30, 2021.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company reviews its long-lived assets for impairment at least annually or when the Company determines a triggering event has occurred. When a triggering event has occurred, each impairment test is based on a comparison of the future expected undiscounted cash flow to the recorded value of the asset. If the recorded value of the asset is less than the undiscounted cash flow, the asset is written down to its estimated fair value. No impairments were recorded for the three and nine months ended September 30, 2021 and 2020.
Warrant Liabilities	Warrant Liabilities The Company’s outstanding warrants include publicly-traded warrants (the “Public Warrants”) which were issued as one-third Derivatives and Hedging-Contracts in Entity’s Own Equity
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements Accounting pronouncements issued but not yet adopted In February 2016, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) 2016-02, Leases (Topic 842) , Revenue from Contracts with Customers (Topic 606) and Leases (Topic 842): Effective Dates for Certain Entities, In August 2018, the FASB issued ASU 2018-15, Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that Is a Service Contract In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes In August 2020, the FASB issued ASU 2020-06, Debt-Debt with Conversion and Other Options (Subtopic 470-20) Derivatives and Hedging-Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity

FAIR VALUE OF FINANCIAL INSTR_2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	9 Months Ended
	Sep. 30, 2021
FAIR VALUE OF FINANCIAL INSTRUMENTS [Abstract]
Assets and Liabilities Measured at Fair Value on Recurring Basis	The following table summarizes the Company’s assets and liabilities that are measured at fair value on a recurring basis, by level, within the fair value hierarchy as of September 30, 2021: Fair Value Measurement Level Total Level 1 Level 2 Level 3 September 30, 2021: Assets: Mutual funds - Cash and cash equivalents $ 59,896 $ 59,896 $ - $ - Mutual funds - Marketable securities 438,102 438,102 - - Total assets at fair value on a recurring basis $ 497,998 $ 497,998 $ - $ - Liabilities: Public Warrants $ 7,782 $ 7,782 $ - $ - Private Warrants 394 - - 394 Total liabilities at fair value on a recurring basis $ 8,176 $ 7,782 $ - $ 394

PROPERTY AND EQUIPMENT, NET (Ta

PROPERTY AND EQUIPMENT, NET (Tables)	9 Months Ended
	Sep. 30, 2021
PROPERTY AND EQUIPMENT, NET [Abstract]
Property and Equipment, Net	Property and equipment, net, are recorded at historical cost and consist of the following: September 30, December 31, Laboratory equipment $ 5,885 $ 4,245 Computer equipment 996 765 Software 156 136 Furniture and fixtures 47 47 Leasehold improvements 22 - Construction in process 1,045 35 8,151 5,228 Less: Accumulated depreciation (3,944 ) (3,232 ) Property and equipment, net $ 4,207 $ 1,996

ACCRUED EXPENSES AND OTHER CU_2

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Tables)	9 Months Ended
	Sep. 30, 2021
ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES [Abstract]
Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consist of the following: September 30, December 31, Employee compensation $ 1,703 $ 511 Contracted services 1,114 399 Legal fees 1,147 447 Other 60 68 Total accrued expenses and other current liabilities $ 4,024 $ 1,425

CONVERTIBLE PREFERRED STOCK (Ta

CONVERTIBLE PREFERRED STOCK (Tables)	9 Months Ended
	Sep. 30, 2021
CONVERTIBLE PREFERRED STOCK [Abstract]
Convertible Preferred Stock	The Company had issued five series of convertible preferred stock, Series A through Series E (the “Convertible Preferred Stock”). The following table summarizes the authorized, issued and outstanding Convertible Preferred Stock of the Company immediately prior to the Business Combination and as of December 31, 2020: Class Year of Class Issuance Issuance Price per Share Shares Authorized Shares Issued and Outstanding Total Proceeds or Exchange Value Issuance Costs Net Carrying Value Initial Liquidation Price per Share Series A 2013 $ 0.04 25,000,000 25,000,000 $ 1,000 $ - $ 1,000 $ 0.80 Series B 2015 0.80 31,250,000 31,250,000 25,000 - 25,000 0.80 Series C 2015 2016 4.61 8,164,323 8,164,323 37,638 328 37,310 4.61 Series D 2017 4.71 12,738,853 12,738,853 60,000 414 59,586 4.71 Series E 2018 2020 5.36 14,925,373 13,636,092 73,089 171 72,918 5.36 92,078,549 90,789,268

EQUITY INCENTIVE PLAN (Tables)

EQUITY INCENTIVE PLAN (Tables)	9 Months Ended
	Sep. 30, 2021
EQUITY INCENTIVE PLAN [Abstract]
Stock Option Activity	A summary of the stock option activity under the 2013 Plan and the 2021 Plan is presented in the table below: Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value Outstanding at December 31, 2020 7,369,541 $ 2.37 6.77 $ 4,094 Granted 3,104,585 9.07 Exercised (2,163,932 ) 2.03 Forfeited (184,017 ) 8.64 Outstanding at September 30, 2021 8,126,177 $ 4.88 7.59 $ 30,222 Options exercisable at September 30, 2021 4,371,817 2.61 6.21 $ 25,100 Vested and expected to vest at September 30, 2021 7,805,361 $ 4.78 7.53 $ 29,784
Restricted Stock Activity	A summary of the RSU activity under the 2013 Plan and the 2021 Plan is presented in the table below: Number of Shares Underlying RSUs Weighted Average Grant- Date Fair Value Outstanding non-vested RSUs at December 31, 2020 - $ - Granted 4,861,315 8.03 Repurchased - - Restrictions lapsed - - Outstanding non-vested RSUs at September 30, 2021 4,861,315 $ 8.03
Stock-Based Compensation Expense	The Company’s stock-based compensation expense is allocated to the following operating expense categories as follows: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 Research and development $ 1,520 $ 355 $ 4,343 $ 1,217 General and administrative 5,626 64 12,918 160 Sales and marketing 250 74 579 224 Total stock-based compensation expense $ 7,396 $ 493 $ 17,840 $ 1,601

NET LOSS PER SHARE (Tables)

NET LOSS PER SHARE (Tables)	9 Months Ended
	Sep. 30, 2021
NET LOSS PER SHARE [Abstract]
Basic and Diluted Net Loss Per Share	The following table presents the calculation of basic and diluted net loss per share for the Company’s common stock: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 Numerator Net loss $ (18,091 ) $ (8,557 ) $ (65,567 ) $ (27,068 ) Numerator for basic and diluted EPS - loss attributable to common stockholders $ (18,091 ) $ (8,557 ) $ (65,567 ) $ (27,068 ) Denominator Common stock 136,456,848 5,360,497 60,104,891 5,350,771 Denominator for basic and diluted EPS - weighted-average common stock 136,456,848 5,360,497 60,104,891 5,350,771 Basic and diluted net loss per share $ (0.13 ) $ (1.60 ) $ (1.09 ) $ (5.06 )
Anti-Dilutive Common Equivalent Shares	Since the Company was in a net loss position for all periods presented, the basic net loss per shares calculation excludes preferred stock as it does not participate in net losses of the Company. Additionally, net loss per share attributable to Class A and Class B common stockholders was the same on a basic and diluted basis, as the inclusion of all potential common equivalent shares outstanding would have been anti-dilutive. Anti-dilutive common equivalent shares were as follows: Three months ended September 30, Nine months ended September 30, 2021 2020 2021 2020 Outstanding options to purchase common stock 8,126,177 7,978,697 8,126,177 7,978,697 Outstanding restricted stock units 4,861,315 - 4,861,315 - Outstanding warrants 3,968,319 - 3,968,319 - Outstanding convertible preferred stock (Series A through E) - 68,684,758 - 68,684,758 16,955,811 76,663,455 16,955,811 76,663,455
Adjustments to Previously Issued Basic and Diluted Net Loss Per Share	The adjustments to the Company’s previously issued condensed consolidated statements of operations and comprehensive loss and Note 10 to our Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2021 are as follows: Three months ended June 30, 2021 Six months ended June 30, 2021 As Reported As Revised As Reported As Revised Denominator Common stock 11,696,084 36,890,502 8,629,355 21,296,162 Denominator for basic and diluted EPS - weighted-average common stock 11,696,084 36,890,502 8,629,355 21,296,162 Basic and diluted net loss per share $ (3.05 ) $ (0.97 ) $ (5.50 ) $ (2.23 )

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	9 Months Ended
	Sep. 30, 2021
COMMITMENTS AND CONTINGENCIES [Abstract]
Future Minimum Rental Payments under Non-cancelable Operating Lease	The following is a schedule of future minimum rental payments under a non-cancelable operating lease with initial terms in excess of one year: Years ending December 31: Remainder of 2021 $ 264 2022 1,186 2023 1,463 2024 1,507 2025 1,552 Thereafter 3,245 Total future minimum rental payments $ 9,217

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 09, 2020
Investments in Marketable Securities [Abstract]
Unrealized losses on marketable securities	$ (634)		$ (634)
Impairment of Long-Lived Assets [Abstract]
Impairments	$ 0	$ 0	$ 0	$ 0
Warrant Liabilities [Abstract]
Number of warrants issued per unit issued during IPO (in shares)					0.33

BUSINESS COMBINATION (Details)

BUSINESS COMBINATION (Details)	Jun. 10, 2021USD ($)$ / sharesshares	Jun. 09, 2021shares	Sep. 30, 2021USD ($)Vote	Feb. 18, 2021USD ($)	Dec. 31, 2020USD ($)
Business Combination [Abstract]
Increase in cash	$ 540,276,000
Warrant liabilities	11,618,000		$ 8,176,000		$ 0
PIPE Investors [Member]
Business Combination [Abstract]
Increase in cash	$ 425,001,000
Class A Common Stock [Member]
Business Combination [Abstract]
Exchange Ratio			0.7975
Class B Common Stock [Member]
Business Combination [Abstract]
Exchange Ratio			0.7975
HighCape [Member]
Business Combination [Abstract]
Exchange Ratio				0.7975
Base amount included in numerator of Exchange Ratio calculation				$ 810,000,000
Expense threshold included in numerator of Exchange Ratio calculation				8,025,000
Denominator included in Exchange Ratio calculation				$ 10
Percentage of combined voting power held by Sponsor	80.40%
Increase in cash	$ 115,275,000
Transaction costs	17,824,000
Payment of PPP loan, including interest	1,764,000
Payments to redeeming shareholders	5,712,000
Payment to third party service provider	3,800,000
Proceeds on date of Business Combination, excluding warrant liabilities and other insignificant assets and liabilities	511,176,000
Warrant liabilities	11,618,000
Transaction costs expensed			$ 7,383,000
Other liabilities and related transaction costs	$ 21,776,000
Net equity infusion from the Business Combination			$ 501,170,000
HighCape [Member] | Foresite Funds [Member]
Business Combination [Abstract]
Shares outstanding (in shares) | shares		696,250
HighCape [Member] | Initial Stockholders [Member]
Business Combination [Abstract]
Shares outstanding (in shares) | shares		2,178,750
HighCape [Member] | Class A Common Stock [Member]
Business Combination [Abstract]
Votes per share | Vote			1
Shares outstanding (in shares) | shares	116,463,160
HighCape [Member] | Class A Common Stock [Member] | Legacy Quantum-Si Stockholders [Member]
Business Combination [Abstract]
Shares outstanding (in shares) | shares	59,754,288
HighCape [Member] | Class A Common Stock [Member] | PIPE Investors [Member]
Business Combination [Abstract]
Shares issued (in shares) | shares	42,500,000
Share price (in dollars per share) | $ / shares	$ 10
Shares outstanding (in shares) | shares	42,500,000
HighCape [Member] | Class A Common Stock [Member] | Foresite Funds [Member]
Business Combination [Abstract]
Shares issued (in shares) | shares	696,250
Share price (in dollars per share) | $ / shares	$ 0.001
Aggregate gross proceeds	$ 1,000
Shares outstanding (in shares) | shares	696,250
HighCape [Member] | Class A Common Stock [Member] | Initial Stockholders [Member]
Business Combination [Abstract]
Shares outstanding (in shares) | shares	2,178,750
HighCape [Member] | Class A Common Stock [Member] | Sponsor [Member]
Business Combination [Abstract]
Shares outstanding (in shares) | shares	405,000
HighCape [Member] | Class A Common Stock [Member] | Public Stockholders [Member]
Business Combination [Abstract]
Shares outstanding (in shares) | shares	10,928,872
Shares redeemed (in shares) | shares	571,128
HighCape [Member] | Class B Common Stock [Member]
Business Combination [Abstract]
Votes per share | Vote			20
Shares outstanding (in shares) | shares	19,937,500
HighCape [Member] | Class B Common Stock [Member] | Minimum [Member]
Business Combination [Abstract]
Percentage of total shares that must be beneficially owned included in sunset provision			20.00%
HighCape [Member] | Class B Common Stock [Member] | Sponsor [Member]
Business Combination [Abstract]
Shares forfeited (in shares) | shares		696,250

FAIR VALUE OF FINANCIAL INSTR_3

FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2021USD ($)$ / shares	Sep. 30, 2021USD ($)$ / shares	Dec. 31, 2020USD ($)
Fair Value Asset Transfers [Abstract]
Transfers from Level 1 to Level 2	$ 0	$ 0	$ 0
Transfers from Level 2 to Level 1	0	0	0
Transfers into Level 3	0	0	0
Transfers out of Level 3	0	0	0
Fair Value Liability Transfers [Abstract]
Transfers from Level 1 to Level 2	0	0	0
Transfers from Level 2 to Level 1	0	0	0
Transfers into Level 3	0	0	0
Transfers out of Level 3	0	0	0
Recurring [Member]
Assets [Abstract]
Mutual funds - Cash and cash equivalents	59,896	59,896
Mutual funds - Marketable securities	438,102	438,102
Total assets	497,998	497,998
Liabilities [Abstract]
Total liabilities	8,176	8,176
Recurring [Member] | Level 1 [Member]
Assets [Abstract]
Mutual funds - Cash and cash equivalents	59,896	59,896	$ 36,040
Mutual funds - Marketable securities	438,102	438,102
Total assets	497,998	497,998
Liabilities [Abstract]
Total liabilities	7,782	7,782
Recurring [Member] | Level 2 [Member]
Assets [Abstract]
Mutual funds - Cash and cash equivalents	0	0
Mutual funds - Marketable securities	0	0
Total assets	0	0
Liabilities [Abstract]
Total liabilities	0	0
Recurring [Member] | Level 3 [Member]
Assets [Abstract]
Mutual funds - Cash and cash equivalents	0	0
Mutual funds - Marketable securities	0	0
Total assets	0	0
Liabilities [Abstract]
Total liabilities	394	394
Recurring [Member] | Private Warrants [Member]
Liabilities [Abstract]
Warrants	394	394
Recurring [Member] | Private Warrants [Member] | Level 1 [Member]
Liabilities [Abstract]
Warrants	0	0
Recurring [Member] | Private Warrants [Member] | Level 2 [Member]
Liabilities [Abstract]
Warrants	0	0
Recurring [Member] | Private Warrants [Member] | Level 3 [Member]
Liabilities [Abstract]
Warrants	394	394
Recurring [Member] | Public Warrants [Member]
Liabilities [Abstract]
Warrants	7,782	7,782
Recurring [Member] | Public Warrants [Member] | Level 1 [Member]
Liabilities [Abstract]
Warrants	7,782	7,782
Recurring [Member] | Public Warrants [Member] | Level 2 [Member]
Liabilities [Abstract]
Warrants	0	0
Recurring [Member] | Public Warrants [Member] | Level 3 [Member]
Liabilities [Abstract]
Warrants	$ 0	$ 0
Warrants [Member] | Private Warrants [Member] | Volatility [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants measurement input	0.523	0.523
Warrants [Member] | Private Warrants [Member] | Risk-Free Interest Rate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants measurement input	0.0091	0.0091
Warrants [Member] | Private Warrants [Member] | Strike Price [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants measurement input | $ / shares	11.50	11.50
Warrants [Member] | Private Warrants [Member] | Share Price [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants measurement input | $ / shares	8.34	8.34
Warrants [Member] | Private Warrants [Member] | Expected Life [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrants term	4 years 8 months 12 days	4 years 8 months 12 days

PROPERTY AND EQUIPMENT, NET (De

PROPERTY AND EQUIPMENT, NET (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Property and Equipment, Net [Abstract]
Property and equipment, gross	$ 8,151		$ 8,151		$ 5,228
Less: Accumulated depreciation	(3,944)		(3,944)		(3,232)
Property and equipment, net	4,207		4,207		1,996
Depreciation and amortization expense	264	$ 222	712	$ 676
Laboratory Equipment [Member]
Property and Equipment, Net [Abstract]
Property and equipment, gross	5,885		5,885		4,245
Computer Equipment [Member]
Property and Equipment, Net [Abstract]
Property and equipment, gross	996		996		765
Software [Member]
Property and Equipment, Net [Abstract]
Property and equipment, gross	156		156		136
Furniture and Fixtures [Member]
Property and Equipment, Net [Abstract]
Property and equipment, gross	47		47		47
Leasehold Improvements [Member]
Property and Equipment, Net [Abstract]
Property and equipment, gross	22		22		0
Construction in Process [Member]
Property and Equipment, Net [Abstract]
Property and equipment, gross	$ 1,045		$ 1,045		$ 35

ACCRUED EXPENSES AND OTHER CU_3

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Accounts Expenses and Other Current Liabilities [Abstract]
Employee compensation	$ 1,703	$ 511
Contracted service	1,114	399
Legal fees	1,147	447
Other	60	68
Total accrued expenses and other current liabilities	$ 4,024	$ 1,425

NOTES PAYABLE (Details)

NOTES PAYABLE (Details) - USD ($) $ in Thousands	Aug. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
NOTES PAYABLE [Abstract]
Loan proceeds received	$ 1,749	$ 0	$ 1,749

CONVERTIBLE PREFERRED STOCK (De

CONVERTIBLE PREFERRED STOCK (Details) $ / shares in Units, $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2021USD ($)$ / sharesshares	Sep. 30, 2020USD ($)shares	Dec. 31, 2020USD ($)Series$ / sharesshares	Jun. 30, 2021USD ($)shares	Mar. 31, 2021USD ($)shares	Jun. 30, 2020USD ($)shares	Mar. 31, 2020USD ($)shares	Dec. 31, 2019USD ($)shares
CONVERTIBLE PREFERRED STOCK [Abstract]
Number of issued series of convertible preferred stock | Series			5
Convertible Preferred Stock [Abstract]
Issuance price per share (in dollars per share) | $ / shares	$ 0.0001		$ 0.0001
Shares authorized (in shares)	0		92,078,549
Shares issued (in shares)	0		90,789,268
Shares outstanding (in shares)	0	86,125,089	90,789,268	0	90,789,268	86,125,089	86,125,089	84,201,570
Total proceeds or exchange value | $	$ 0	$ 10,310
Net carrying value | $	$ 0	$ 170,831	$ 195,814	$ 0	$ 195,810	$ 170,831	$ 170,843	$ 160,555
Series A [Member]
Convertible Preferred Stock [Abstract]
Year of class issuance			2013
Issuance price per share (in dollars per share) | $ / shares			$ 0.04
Shares authorized (in shares)			25,000,000
Shares issued (in shares)			25,000,000
Shares outstanding (in shares)			25,000,000
Total proceeds or exchange value | $			$ 1,000
Issuance costs | $			0
Net carrying value | $			$ 1,000
Initial liquidation price per share (in dollars per share) | $ / shares			$ 0.80
Series B [Member]
Convertible Preferred Stock [Abstract]
Year of class issuance			2015
Issuance price per share (in dollars per share) | $ / shares			$ 0.80
Shares authorized (in shares)			31,250,000
Shares issued (in shares)			31,250,000
Shares outstanding (in shares)			31,250,000
Total proceeds or exchange value | $			$ 25,000
Issuance costs | $			0
Net carrying value | $			$ 25,000
Initial liquidation price per share (in dollars per share) | $ / shares			$ 0.80
Series C [Member]
Convertible Preferred Stock [Abstract]
Issuance price per share (in dollars per share) | $ / shares			$ 4.61
Shares authorized (in shares)			8,164,323
Shares issued (in shares)			8,164,323
Shares outstanding (in shares)			8,164,323
Total proceeds or exchange value | $			$ 37,638
Issuance costs | $			328
Net carrying value | $			$ 37,310
Initial liquidation price per share (in dollars per share) | $ / shares			$ 4.61
Series C [Member] | Minimum [Member]
Convertible Preferred Stock [Abstract]
Year of class issuance			2015
Series C [Member] | Maximum [Member]
Convertible Preferred Stock [Abstract]
Year of class issuance			2016
Series D [Member]
Convertible Preferred Stock [Abstract]
Year of class issuance			2017
Issuance price per share (in dollars per share) | $ / shares			$ 4.71
Shares authorized (in shares)			12,738,853
Shares issued (in shares)			12,738,853
Shares outstanding (in shares)			12,738,853
Total proceeds or exchange value | $			$ 60,000
Issuance costs | $			414
Net carrying value | $			$ 59,586
Initial liquidation price per share (in dollars per share) | $ / shares			$ 4.71
Series E [Member]
Convertible Preferred Stock [Abstract]
Issuance price per share (in dollars per share) | $ / shares			$ 5.36
Shares authorized (in shares)			14,925,373
Shares issued (in shares)			13,636,092
Shares outstanding (in shares)			13,636,092
Total proceeds or exchange value | $			$ 73,089
Issuance costs | $			171
Net carrying value | $			$ 72,918
Initial liquidation price per share (in dollars per share) | $ / shares			$ 5.36
Series E [Member] | Minimum [Member]
Convertible Preferred Stock [Abstract]
Year of class issuance			2018
Series E [Member] | Maximum [Member]
Convertible Preferred Stock [Abstract]
Year of class issuance			2020
Class A Common Stock [Member]
Convertible Preferred Stock [Abstract]
Exchange Ratio	0.7975
Class B Common Stock [Member]
Convertible Preferred Stock [Abstract]
Exchange Ratio	0.7975

EQUITY INCENTIVE PLAN, Stock Op

EQUITY INCENTIVE PLAN, Stock Option Activity (Details) - 2013 and 2021 Plans [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2021	Dec. 31, 2020
Stock Options [Member]
Stock Option Activity [Abstract]
Stock-based compensation expense	$ 1,556		$ 4,608
Number of Options [Roll Forward]
Outstanding, beginning balance (in shares)		7,369,541	7,369,541
Granted (in shares)			3,104,585
Exercised (in shares)			(2,163,932)
Forfeited (in shares)			(184,017)
Outstanding, ending balance (in shares)	8,126,177		8,126,177	7,369,541
Options exercisable (in shares)	4,371,817		4,371,817
Vested and expected to vest (in shares)	7,805,361		7,805,361
Weighted Average Exercise Price [Roll Forward]
Outstanding, beginning balance (in dollars per share)		$ 2.37	$ 2.37
Granted (in dollars per share)			9.07
Exercised (in dollars per share)			2.03
Forfeited (in dollars per share)			8.64
Outstanding, ending balance (in dollars per share)	$ 4.88		4.88	$ 2.37
Options exercisable (in dollars per share)	2.61		2.61
Vested and expected to vest (in dollars per share)	$ 4.78		$ 4.78
Weighted Average Remaining Contractual Term and Aggregate Intrinsic Value [Abstract]
Weighted average remaining contractual term, outstanding			7 years 7 months 2 days	6 years 9 months 7 days
Weighted average remaining contractual term, options exercisable			6 years 2 months 15 days
Weighted average remaining contractual term, vested and expected to vest			7 years 6 months 10 days
Aggregate intrinsic value, outstanding, beginning balance		$ 4,094	$ 4,094
Aggregate intrinsic value, outstanding, ending balance	$ 30,222		30,222	$ 4,094
Aggregate intrinsic value, options exercisable	25,100		25,100
Aggregate intrinsic value, vested and expected to vest	$ 29,784		29,784
Stock Options Subject to Service and/or Performance Conditions [Member]
Stock Option Activity [Abstract]
Stock-based compensation expense		$ 1,343	$ 2,381

EQUITY INCENTIVE PLAN, Restrict

EQUITY INCENTIVE PLAN, Restricted Stock Unit Activity (Details) - 2013 and 2021 Plans [Member] $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended	9 Months Ended
	Sep. 30, 2021USD ($)$ / sharesshares	Jun. 30, 2021USD ($)$ / sharesshares	Sep. 30, 2021USD ($)Director$ / sharesshares
RSU Awards [Member]
Restricted Stock Unit Activity [Abstract]
Number of members of board of directors receiving grant of RSU award | Director			2
Stock-based compensation expense | $	$ 5,840		$ 13,232
Number of Shares Underlying RSUs [Roll Forward]
Outstanding non-vested RSUs, beginning balance (in shares)		0	0
Granted (in shares)			4,861,315
Repurchased (in shares)			0
Restrictions lapsed (in shares)			0
Outstanding non-vested RSUs, ending balance (in shares)	4,861,315		4,861,315
Weighted Average Grant-Date Fair Value [Abstract]
Outstanding non-vested RSUs, beginning balance (in dollars per share) | $ / shares		$ 0	$ 0
Granted (in dollars per share) | $ / shares			8.03
Repurchased (in dollars per share) | $ / shares			0
Restrictions lapsed (in dollars per share) | $ / shares			0
Outstanding non-vested RSUs, ending balance (in dollars per share) | $ / shares	$ 8.03		$ 8.03
RSU Awards Subject to Service and Performance Conditions [Member] | Chief Executive Officer [Member]
Number of Shares Underlying RSUs [Roll Forward]
Granted (in shares)			1,703,460
RSU Awards Subject to Service and Performance Conditions [Member] | General Counsel [Member]
Number of Shares Underlying RSUs [Roll Forward]
Granted (in shares)			170,346
Restricted Stock Units Subject to Service and/or Performance Condition [Member] | Executive Chairman and Two Members of Board of Directors [Member]
Number of Shares Underlying RSUs [Roll Forward]
Granted (in shares)			1,800,000
RSU Awards Subject to Service, Market and Performance Conditions [Member]
Restricted Stock Unit Activity [Abstract]
Stock-based compensation expense | $		$ 7,393	$ 13,089
RSU Awards Subject to Service, Market and Performance Conditions [Member] | Chief Executive Officer [Member]
Number of Shares Underlying RSUs [Roll Forward]
Granted (in shares)			453,777

EQUITY INCENTIVE PLAN, Stock-Ba

EQUITY INCENTIVE PLAN, Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Stock-Based Compensation Expense [Abstract]
Stock-based compensation expense	$ 7,396	$ 493	$ 17,840	$ 1,601
Research and Development [Member]
Stock-Based Compensation Expense [Abstract]
Stock-based compensation expense	1,520	355	4,343	1,217
General and Administrative [Member]
Stock-Based Compensation Expense [Abstract]
Stock-based compensation expense	5,626	64	12,918	160
Sales and Marketing [Member]
Stock-Based Compensation Expense [Abstract]
Stock-based compensation expense	$ 250	$ 74	$ 579	$ 224

NET LOSS PER SHARE (Details)

NET LOSS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						6 Months Ended	9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Sep. 30, 2021	Sep. 30, 2020
Numerator [Abstract]
Net loss	$ (18,091)	$ (35,697)	$ (11,779)	$ (8,557)	$ (8,197)	$ (10,314)		$ (65,567)	$ (27,068)
Numerator for basic EPS - loss attributable to common stockholders	(18,091)			(8,557)				(65,567)	(27,068)
Numerator for diluted EPS - loss attributable to common stockholders	$ (18,091)			$ (8,557)				$ (65,567)	$ (27,068)
Denominator [Abstract]
Common stock (in shares)	136,456,848			5,360,497				60,104,891	5,350,771
Denominator for basic EPS - weighted-average common stock (in shares)	136,456,848			5,360,497				60,104,891	5,350,771
Denominator for diluted EPS - weighted-average common stock (in shares)	136,456,848			5,360,497				60,104,891	5,350,771
Basic net loss per share (in dollars per share)	$ (0.13)			$ (1.60)				$ (1.09)	$ (5.06)
Diluted net loss per share (in dollars per share)	$ (0.13)			$ (1.60)				$ (1.09)	$ (5.06)
Net Loss per Share [Abstract]
Anti-dilutive common equivalent shares (in shares)	16,955,811			76,663,455				16,955,811	76,663,455
Outstanding Convertible Preferred Stock (Series A through E) [Member]
Net Loss per Share [Abstract]
Anti-dilutive common equivalent shares (in shares)	0			68,684,758				0	68,684,758
Misstatement in Basic and Diluted Net Loss per Share Calculation [Member]
Denominator [Abstract]
Common stock (in shares)		36,890,502					21,296,162
Denominator for basic EPS - weighted-average common stock (in shares)		36,890,502					21,296,162
Denominator for diluted EPS - weighted-average common stock (in shares)		36,890,502					21,296,162
Basic net loss per share (in dollars per share)		$ (0.97)					$ (2.23)
Diluted net loss per share (in dollars per share)		$ (0.97)					$ (2.23)
Misstatement in Basic and Diluted Net Loss per Share Calculation [Member] | Previously Reported [Member]
Denominator [Abstract]
Common stock (in shares)		11,696,084					8,629,355
Denominator for basic EPS - weighted-average common stock (in shares)		11,696,084					8,629,355
Denominator for diluted EPS - weighted-average common stock (in shares)		11,696,084					8,629,355
Basic net loss per share (in dollars per share)		$ (3.05)					$ (5.50)
Diluted net loss per share (in dollars per share)		$ (3.05)					$ (5.50)
Outstanding Options to Purchase Common Stock [Member]
Net Loss per Share [Abstract]
Anti-dilutive common equivalent shares (in shares)	8,126,177			7,978,697				8,126,177	7,978,697
Outstanding Restricted Stock Units [Member]
Net Loss per Share [Abstract]
Anti-dilutive common equivalent shares (in shares)	4,861,315			0				4,861,315	0
Outstanding Warrants [Member]
Net Loss per Share [Abstract]
Anti-dilutive common equivalent shares (in shares)	3,968,319			0				3,968,319	0

WARRANT LIABILITIES (Details)

WARRANT LIABILITIES (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 10, 2021	Dec. 31, 2020
Warrants [Abstract]
Fair value of warrant liabilities	$ 8,176		$ 8,176		$ 11,618	$ 0
Change in fair value of warrant liabilities	$ 6,975	$ 0	$ 3,442	$ 0
Public Warrants [Member]
Warrants [Abstract]
Warrants outstanding (in shares)	3,833,319		3,833,319
Number of shares to be issued upon exercise of warrant (in shares)	1		1
Exercise price of warrant (in dollars per share)	$ 11.50		$ 11.50
Warrant redemption price (in dollars per share)	0.01		$ 0.01
Notice period to redeem warrants			30 days
Share price (in dollars per share)	$ 18		$ 18
Threshold trading days			20 days
Threshold consecutive trading days			30 days
Period prior to notice of redemption			3 days
Trading day period to calculate fair market value over exercise price of warrants			10 days
Beneficial ownership percentage			50.00%
Warrants exercised (in shares)	0		0
Warrants redeemed (in shares)	0		0
Private Warrants [Member]
Warrants [Abstract]
Warrants outstanding (in shares)	135,000		135,000
Warrant redemption price (in dollars per share)	$ 0.01		$ 0.01
Limitation period to transfer, assign or sell warrants			30 days
Warrants exercised (in shares)	0		0
Warrants redeemed (in shares)	0		0

INCOME TAXES (Details)

INCOME TAXES (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
INCOME TAXES [Abstract]
Estimated annual effective tax rate	0.00%	0.00%	0.00%	0.00%
Federal statutory rate	21.00%	21.00%	21.00%	21.00%

RELATED PARTY TRANSACTIONS (Det

RELATED PARTY TRANSACTIONS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Related Party Transactions [Abstract]
Period after end of month when related party balances are paid or received			30 days
Related Party [Member] | Leasing of Office and Laboratory Space [Member]
Related Party Transactions [Abstract]
Payments to related party	$ 80	$ 241	$ 80	$ 241
4C [Member] | Leasing of Office and Laboratory Space [Member]
Related Party Transactions [Abstract]
Payments to related party	36	36	112	117
4C [Member] | Prefunding of Acquisition of Certain Shared Capital Assets [Member] | Other Assets [Member]
Related Party Transactions [Abstract]
Payments to related party	0		0		$ 738
4C [Member] | Monthly Services Under Amended and Restated Technology Services Agreement [Member]
Related Party Transactions [Abstract]
Related party expenses	203	$ 396	1,782	$ 1,073
4C [Member] | Monthly Services Under Amended and Restated Technology Services Agreement [Member] | Prepaid Expenses and Other Current Assets [Member]
Related Party Transactions [Abstract]
Due from related parties	0		0		13
4C and Other Companies Controlled by Rothberg Family [Member] | Termination of ARTSA [Member]
Related Party Transactions [Abstract]
Related party expenses			700
Other Companies Controlled by Rothberg Family [Member] | Payments Made to Third Parties on Behalf of the Company Under ARTSA [Member] | Accounts Payable [Member]
Related Party Transactions [Abstract]
Due to related parties	170		170		28
Other Companies Controlled by Rothberg Family [Member] | Payments Made to Third Parties on Behalf of Other Entities Under ARTSA [Member] | Prepaid Expenses and Other Current Assets [Member]
Related Party Transactions [Abstract]
Due from related parties	158		158		69
PEI [Member] | Binders Collaboration [Member]
Related Party Transactions [Abstract]
Payments to related party	0		0
President and Chief Operating Officer and Other Company Employees [Member] | Promissory Notes [Member]
Related Party Transactions [Abstract]
Due from related parties	0		0		$ 150
Dr. Rothberg [Member] | Executive Chairman Agreement [Member]
Related Party Transactions [Abstract]
Payments to related party	$ 25		25
Annual amount of transaction with related party			$ 400

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Capital Leases [Abstract]
Value of equipment acquired through capital lease arrangements	$ 124		$ 124
Interest expense under capital lease arrangements	0	$ 1	1	$ 5
Unamortized balance of equipment acquired through capital lease arrangements	0		0
Future Minimum Lease Payments under Non-cancelable Operating Lease [Abstract]
Remainder of 2021	264		264
2022	1,186		1,186
2023	1,463		1,463
2024	1,507		1,507
2025	1,552		1,552
Thereafter	3,245		3,245
Total future minimum rental payments	9,217		9,217
Licenses Related to Certain Intellectual Property [Abstract]
Annual minimum fixed payments	220		220
Other Commitments [Abstract]
Employer matching contributions to 401(k) plan	$ 0	$ 0	0	$ 0
HighCape [Member]
Contingencies [Abstract]
Payment to third party service provider in connection with Business Combination			$ 3,800

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - Subsequent Event [Member] - Majelac [Member] $ in Thousands	Nov. 05, 2021USD ($)shares
Subsequent Events [Abstract]
Cash paid	$ 5,000
Reimbursement for certain recently purchased equipment	132
Earn-out payments	$ 800
Percentage of cash and shares held back at closing	0.10
Class A Common Stock [Member]
Subsequent Events [Abstract]
Shares issued (in shares) | shares	595,562