Note 13 - Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Notes Tables

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

	Year Ended
	December 31,
	2020			2019
U.S. federal statutory rate, beginning of year		21	%		21	%
Officers' compensation		2			7
Other		(3	)		(2	)
Valuation allowance		(20	)		(26	)
Effective tax rate as reported		—	%		—	%

Schedule of Deferred Tax Assets and Liabilities [Table Text Block]

	Year Ended
	December 31,
	2020			2019
Deferred tax assets
Net operating loss carryforwards and credits	$	20,698		$	15,064
Share-based compensation expense		3,813			3,441
Property, plant and equipment		725			1,025
Common stock warrant liabilities		—			524
Operating lease liabilities		91			147
Other		54			21
Less: valuation allowance		(22,669	)		(19,802	)
Total deferred tax assets		2,712			420
Deferred tax liabilities
Common stock warrant liabilities		(1,129	)		—
Operating lease Right-of-use assets		(1,583	)		(420	)
Total deferred tax liabilities		(2,712	)		(420	)
Net deferred tax assets (liabilities)	$	—		$	—