Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 38,517	$ 10,218
Short-term investments	997	19,022
Accounts receivable, net	1,186	1,731
Inventory	233	252
Prepaid expenses and other current assets	2,807	1,264
Total current assets	43,740	32,487
Property and equipment, net	15,022	14,911
Operating lease right-of-use assets	4,142	4,590
Intangible assets, net	683	731
Goodwill	278	278
Other assets	598	602
TOTAL ASSETS	64,463	53,599
Current liabilities
Accounts payable and accrued expenses	8,026	7,095
Other current liabilities	3,223	2,338
Current portion of long-term note payable	536	528
Deferred revenue	23	98
Total current liabilities	11,808	10,059
Common stock warrant liability	7,145
Operating lease liabilities	2,614	2,994
Other long-term liabilities	1,243	1,630
Total liabilities	22,810	14,683
Commitments and Contingencies (Note 12)
STOCKHOLDERS' EQUITY
Preferred stock - 25,000,000 shares authorized, 0 shares issued and outstanding at March 31, 2020 and December 31, 2019
Common stock - $.001 par value; 250,000,000 shares authorized; 38,393,289 and 27,374,653 shares issued and outstanding at March 31, 2020 and December 31, 2019, respectively	38	27
Additional paid-in capital	490,009	474,174
Accumulated other comprehensive income	3	72
Accumulated deficit	(448,397)	(435,357)
Total stockholders' equity	41,653	38,916
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 64,463	$ 53,599