Note 11 - Equity Incentive Plans (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Sep. 30, 2023	Jun. 30, 2023	Aug. 04, 2022	Dec. 31, 2021	Jun. 16, 2021	Jun. 08, 2020	Apr. 23, 2019
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number (in shares)	17,938,726	14,725,261				10,216,106
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 2.9	$ 4.48				$ 4.96
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term (Year)	8 years 2 months 4 days
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Intrinsic Value	$ 26,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Exercisable, Number (in shares)	9,667,285
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 3.17
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term (Year)	7 years 8 months 12 days
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value	$ 26,000
Proceeds from Stock Options Exercised	$ 17,000	$ 223,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period (in shares)	54,720	180,336
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 31,000	$ 481,000
Share Price (in dollars per share)	$ 0.57
Common Stock, Capital Shares Reserved for Future Issuance (in shares)	27,043,664	29,635,697
Proceeds from Stock Plans	$ 562,000	$ 0
Share-Based Payment Arrangement, Expense	$ 14,132,000	$ 13,587,000
Share-Based Payment Arrangement, Option [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)	$ 0.78	$ 4.1
Common Stock, Capital Shares Reserved for Future Issuance (in shares)	17,938,726	14,725,261
Options and RSU [Member]
Share-Based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount	$ 20,500,000
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)	2 years 1 month 17 days
The 2019 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)					28,900,000		16,900,000	8,000,000	1,600,000
The 2022 ESPP [Member]
Share Price (in dollars per share)	$ 0.27		$ 0.54	$ 0.46
Common Stock, Capital Shares Reserved for Future Issuance (in shares)	1,065,325				1,800,000
Proceeds from Stock Plans	$ 600,000
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares)	734,675
Share-Based Payment Arrangement, Expense	$ 400,000
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 100,000