Note 2 - Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2021

Notes Tables

Schedule of Cash and Cash Equivalents [Table Text Block]

	June 30, 2021		December 31, 2020
BioLargo, Inc. and subsidiaries	$	1,338	$	637
Clyra Medical Technologies, Inc.		19		79
Total	$	1,357	$	716

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

	June 30, 2021			June 30, 2020
Customer A		22	%		<10	%
Customer B		19	%		<10	%
Customer C		11	%		<10	%
Customer D		<10	%		13	%

	June 30, 2021			December 31, 2020
Customer C		31	%		<10	%
Customer D		17	%		<10	%
Customer E		11	%		<10	%
Customer F		<10	%		32	%
Customer G		<10	%		10	%

Schedule of Inventory, Current [Table Text Block]

	June 30, 2021		December 31, 2020
Raw material	$	91	$	111
Finished goods		171		166
Total	$	262	$	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	%	123	–	124%	131	%	131	–	133%
Expected dividend yield		—			—		—			—
Forfeiture rate		—			—		—			—
Life in years		10			10		10			10