What is the color of cyanobacteria?
Cyanobacteria are one of the earliest life forms known to have
existed on Earth: stromatolites (which you can see on certain
coastlines) are mounds of fossilised cynabacteria - the oldest ones
to be found are about 3.5 million years old. Because cyanobacteria
perform photosynthesis, they're believed to have been one of the
main contributory factors to the rise in early atmospheric oxygen
levels. Cyanobacteria still exist today; until recently we called
them blue-green algae, & they look remarkably similar to their
early cousins.