Stromatolites are solid, laminar structures reflecting complex interplays between microbial communities and their environment. Hand sample of Dresser Formation stromatolite with domical topography (arrowed). Image credit: Hickman-Lewis et al., doi: 10.1130/G50390.1. The earliest morphological traces of life on Earth are often highly controversial, both because non-biological processes can produce relatively similar structures and because such fossils...