This book describes microbially induced sedimentary structures as new group in the Classification of Primary Sedimentary Structures. Those structures rise from the interaction of benthic microorganisms with physical sediment dynamics caused by waves and currents. We can observe the formation of those features today in modern coastal settings, where the structures are much more common than stromatolites. However, fossil structures occur since the earliest Archean, and are abundant throughout Earth history. The structures constitute a significant archive for the understanding of Earth 's earliest worlds, and are important biosignatures for the detection of life on other planets. This book is for sedimentologists, paleontologists, microbiologists, and geobiologists likewise.