Most Precambrian fossils are of single-celled organisms of bacteria, algae and similar life forms.
Two fundamental types of cells are found in Precambrian rocks. Prokaryotes The earliest fossils are prokaryotes - cells without a nucleus . Modern prokaryotes include bacteria and blue-green algae. Stromatolites are important Precambrian fossils and represent some of the oldest fossils. The Precambrian is the heyday of stromatolites.