Soils would not exist without the complex and heterogeneous activities of microorganisms. For the third volume of Soil Biology, an international board of renowned scientists shed light on the significant role of these organisms. The following key topics are covered: Microorganisms in bioerosion, humification, mineralization and soil aggregation; Microbial energetics and microbes in biogeochemical processes such as carbon and nitrogen cycles and phosphorus bio-availability; Interactions in the mycorrhizosphere, e.g. between mycorrhizal fungi and bacteria; Impact of microbes on plant...