Note 9 - Stockholders' Equity - Shares of Common Stock Reserved for Issuance (Details) - shares	Mar. 31, 2024	Feb. 27, 2024	Dec. 31, 2023
Common stock reserved for issuance (in shares)	29,588,664		27,043,664
Common Warrants [Member]
Common stock reserved for issuance (in shares)	211,259		227,434
The 2019 Plan [Member]
Common stock reserved for issuance (in shares)	1,404,517		5,685,806
The 2024 Inducement Award Plan [Member]
Common stock reserved for issuance (in shares)	1,750,000	3,000,000	0
Share-Based Payment Arrangement, Option [Member]
Common stock reserved for issuance (in shares)	21,843,566		17,938,726
Restricted Stock Units (RSUs) [Member]
Common stock reserved for issuance (in shares)	3,313,997		2,126,373
ESPP [Member]
Common stock reserved for issuance (in shares)	1,065,325		1,065,325