Note 14 - Stock Based Compensation (Tables)

9 Months Ended

Sep. 30, 2021

Notes Tables

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Period ended September 30,
	2021		2020
Risk-free interest rate		0.89%-1.08%		0.28%-0.47%
Expected term (in years)		5.31-6.17		4.50-6.18
Dividend yield		-		-
Expected volatility		122%-130%		103%-129%

Share-based Payment Arrangement, Option, Activity [Table Text Block]

	Number of Underlying Shares			Weighted- Average Exercise Price Per Share		Weighted- Average Contractual Life Remaining in Years		Aggregate Intrinsic Value
Outstanding as of January 1, 2021		7,067,436		$	2.74		-
Granted		3,818,921			2.98		-		99,800
Exercised		(699,410	)		2.46		-		2,753,652
Forfeited		(75,000	)		3.05		-		-
Expired		(223	)		225.00		-		-
Outstanding as of September 30, 2021		10,111,724			2.84		8.53	$	11,697,962
Exercisable as of September 30, 2021		5,663,935			2.94		7.87	$	9,039,985
Vested and expected to vest		10,111,724		$	2.84		8.53	$	11,697,962

Share-based Payment Arrangement, Option [Member]

Notes Tables

Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]

	Three Months Ended September 30,				Nine Months Ended September 30,
	2021		2020		2021		2020
General and administrative	$	1,231,590	$	489,853	$	2,534,117	$	1,675,414
Research and development		562,548		173,740		1,113,882		712,415
Total stock compensation expense	$	1,794,138	$	663,593	$	3,647,999	$	2,387,829