Note 2 - Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2021

Notes Tables

Schedule of Cash and Cash Equivalents [Table Text Block]

	March 31, 2021		December 31, 2020
BioLargo, Inc. and subsidiaries	$	1,304	$	637
Clyra Medical Technologies, Inc.		37		79
Total	$	1,341	$	716

Schedules of Concentration of Risk, by Risk Factor [Table Text Block]

	March 31, 2021			March 31, 2020
Customer A		39	%		<10	%
Customer B		16	%		11	%
Customer C		13	%		<10	%
Customer D		12	%		14	%
Customer E		<10	%		10	%

	March 31, 2021			December 31, 2020
Customer D		29	%		<10	%
Customer E		13	%		<10	%
Customer F		12	%		<10	%
Customer G		<10	%		32	%
Customer H		<10	%		10	%

Schedule of Inventory, Current [Table Text Block]

	March 31, 2021		December 31, 2020
Raw material	$	91	$	111
Finished goods		151		166
Total	$	242	$	277

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

	2021							2020
	Non Plan			2018 Plan				Non Plan			2018 Plan
Risk free interest rate		1.73	%		0.93	–	1.73%		0.88	%		0.88	–	1.90%
Expected volatility		124	%				124%		131	%		131	-	133%
Expected dividend yield		—				—			—				—
Forfeiture rate		—				—			—				—
Life in years		10				10			10				10