Microbe lasagna tells us about what life was like billions of years ago Layers of bacteria and rock leave their fingerprints behind by changing the kinds of carbon atoms we might find in the environment.

Sort of like a fossilized microbial lasagna, fossils called “stromatolites” are formed when layered communities of different types of bacteria trap sand, dirt, and debris in their structure over time. Stromatolites are found in rocks as old as 3.5 billion years, and containing the planet’s earliest life forms.