Note 6 - Stockholders' Equity, Stock Options and Warrants (Tables)

6 Months Ended

Jun. 30, 2021

Notes Tables

Sales of Stock [Table Text Block]

Offering Closing Date	Shares		Sale Price per Share*		Investor Warrants		Exercise Price per Share – Investor Warrants		Placement Agent Warrants		Exercise Price per Share – Placement Agent Warrants		Gross Proceeds of Offering		Net Proceeds of Offering
January 12, 2021 (registered direct)		3,650,840	$	0.842		1,825,420	$	0.80		273,813	$	1.0525	$	3,074,007	$	2,731,766
January 21, 2021 (registered direct)		2,200,000	$	1.00		1,100,000	$	1.00		165,000	$	1.25	$	2,200,000	$	1,932,050
January 26, 2021 (registered direct)		3,414,970	$	1.20		1,707,485	$	1.37		256,123	$	1.50	$	4,097,964	$	3,668,687
February 16, 2021 (registered direct)		4,222,288	$	1.75		2,111,144	$	2.00		316,672	$	2.1875	$	7,389,004	$	6,679,989
February 23, 2021 (private placement)		9,043,766	$	1.95		4,521,883	$	2.00		678,282	$	2.4375	$	17,635,344	$	16,064,739
Total		22,531,864				11,265,932				1,689,890			$	34,396,319	$	31,077,231

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

	Stock Options					Warrants
	Number of Shares			Average Exercise Price		Number of Shares			Average Exercise Price
Outstanding at December 31, 2019		766,424		$	11.34		2,171,610		$	15.26
Issued		319,851			1.03		8,097,468			1.547
Forfeited		(72,728	)		10.58		(128,710	)		95.11
Exercised		-			-		(2,786,992	)		0.79
Outstanding at December 31, 2020		1,013,547		$	5.41		7,353,376		$	3.76
Issued		60,680			1.08		29,640,801			1.44
Forfeited		(60,447	)		8.39		-			-
Exercised		-			-		(5,247,059	)		0.86
Outstanding at June 30, 2021		1,013,780		$	5.07		31,747,118		$	2.077