Note 9 - Income Taxes - Significant Components of the Deferred Tax Assets and Liabilities (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Stock-based compensation	$ 4,514,806	$ 3,768,282
Tax credit carryforwards	1,966,817	1,790,387
Net operating loss carryforwards	19,381,496	11,745,648
Intangible assets	564,880	451,556
Other	637,687	373,314
Total deferred tax assets	27,065,686	18,129,187
Deferred tax liabilities:
Property and equipment	331,231	305,619
Total deferred tax liabilities	331,231	305,619
Net deferred tax assets	26,734,455	17,823,568
Less valuation allowance	(26,734,455)	(17,823,568)
Total deferred tax assets (liabilities)