Note 5 - Income Taxes - Components of Net Deferred Tax Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred Tax Assets
Allowance for doubtful accounts	$ 9	$ 10
Accrued expenses	112	87
Stock-based compensation	265	195
R&D tax credits	1,005	788
Operating lease	1,130	764
PPP Loan expenses	9
NOL Carryforward	97
Total Deferred Tax Assets	2,627	1,844
Deferred Tax Liabilities
Excess of tax over book depreciation and amortization	(1,775)	(1,696)
Prepaid expenses	(48)	(40)
Operating lease	(1,015)	(658)
Total Deferred Tax Liabilities	(2,838)	(2,394)
Net Deferred Tax Liabilities	$ (211)	$ (550)