What is this picture?

Question

What is shown in this image?

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