This book provides information about microbial mats, from early fossils to modern mats located in marine and terrestrial environments. Microbial mats – layered biofilms containing different types of cells – are most complex systems in which representatives of various groups of organisms are found together. Among them are cyanobacteria and eukaryotic phototrophs, aerobic heterotrophic and chemoautotrophic bacteria, protozoa, anoxygenic photosynthetic bacteria, and other types