What is this close-up picture? (WotsThat: algae biofilm on rock)

Question

What object is shown in this zoomed-in close-up photo?

Accepted Answer

algae biofilm on rock. Algae Biofilm Can "Taste" Light Algae biofilms don't just passively sit on rocks—they actively sense which direction light is coming from and physically move toward it, essentially allowing single-celled organisms to "see" without eyes. This cooperative behavior means that what looks like a boring green slime is actually a sophisticated living community making intelligent decisions together about where to grow.

Answer: algae biofilm on rock

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