Arbuscular mycorrhizal fungi are obligate root symbionts that impact plant growth, productivity and competitiveness. The book integrates key information about AMF concepts, structures and functions, and the new classification of Glomeromycota, including topics about AMF history and evolution, AMF families, genus and species description, as well as a compilation about several prools to assess AMF and how to identify them. The focus is to provide readers enough information about AMF.