Note 3 - Summary of Significant Accounting Policies - Potentially Dilutive Securities (Details) - shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Stock Options (in shares)	4,189,006	3,033,047
Warrants (in shares)	6,596,096	7,935,503
Convertible Preferred Stock (in shares)	6,476,275	9,517,191
Total Potential Dilutive Shares (in shares)	17,261,377	20,485,741