Add to ORKGLife may have been present on Earth from about 3.8 Ga or earlier. Based on a combination of geochemical, morphological and sedimentological evidence, the early biosphere included a wide diversity of prokaryotes exhibiting modern metabolisms that thrived in various marine and possibly terrestrial habitats. Among early microorganisms, cyanobacteria played a major role, inventing oxygenic photosynthesis that caused a most profound alteration in our planet. Part of our ongoing work aims to characterize the morphological and geochemical signatures of modern and fossil cyanobacteria and other prokaryotes. Multidisciplinary research, especially on the paleontology of early microorganisms on Earth and the microbiology of extremophiles in recent Ear...