The hotspots of microbial activity in soils such as the rhizosphere, detritusphere, porosphere (including biopores, drillosphere) and aggregatusphere are characterized by high activity rates resulting in accelerated turnover of soil organic matter and other soil microbial functions. The intensity of microbial and SOM turnover in such hotspots is at least one order of magnitude higher than in the bulk soil. This session challenges to estimate the contribution of the hotspots to the whole soil profile and to demonstrate the responsibility of the hotspots for the ecologically relevant processes occurring in soil, such as SOM dynamics, organo-mineral associations and microbial-mineral interactions. Factors influencing the size, activity, interactions, composition and distribution of microbial communities in such hot spots will be discussed, including but not restricted to the availability of resources, soil structure, soil chemistry and microclimatic conditions.