Condensed Statement of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net loss	$ (30,025)	$ (20,650)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,246	305
Non-cash lease expense	249
Non-cash interest expense	140	200
Accretion of discount on investments, net	60	16
Provision for accounts receivable	5	11
Provision for inventories	115	90
Stock-based compensation expense	5,852	580
Change in fair value of redeemable convertible preferred stock warrant liability		(101)
Changes in operating assets and liabilities:
Accounts receivable	(5,646)	(3,055)
Inventories	(7,247)	824
Prepaid expenses and other assets	(981)	71
Accounts payable	1,613	(1,430)
Accrued payroll and related benefits	(4,244)	(2,726)
Accrued expenses and other current liabilities	164	150
Accrued warranty liability	(53)	71
Deferred revenue	305	751
Operating lease liabilities	(169)
Net cash used in operating activities	(38,616)	(24,893)
Cash flows from investing activities:
Purchases of property and equipment	(919)	(2,799)
Purchases of short-term investments	(25,788)
Sales and maturities of short-term investments	19,900	21,958
Net cash (used in) provided by investing activities	(6,807)	19,159
Cash flows from financing activities:
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs		126,758
Proceeds from stock option exercises and employee stock purchase plan purchases	2,218	15
Repayment of finance lease		(3)
Net cash provided by financing activities	2,218	126,770
Net (decrease) increase in cash, cash equivalents and restricted cash	(43,205)	121,036
Cash, cash equivalents and restricted cash as of beginning of period	328,283	37,669
Cash, cash equivalents and restricted cash as of end of period	285,078	158,705
Supplemental cash flow disclosures:
Cash paid for interest	282	800
Cash paid for amounts included in the measurement of operating lease liabilities	169
Supplemental non-cash investing and financing activities:
Capital expenditures included in accounts payable and accrued expenses	$ 238	366
Deemed dividend on settlement of accrued dividend		42,530
Adjustment to redemption value on redeemable convertible preferred stock		362
Issuance of common stock on settlement of accrued dividend		$ 41,763