Microaggregate formation, development and turnover and its linkage to soils functions is a hot topic of scientific debate and intensive research. The term microaggregates refers to all compound soil structures – including the organo-mineral associations – smaller 250 µm (Totsche et al., 2018). During pedogenesis, microaggregates are formed by an interplay of physical, chemical and biological aggregation mechanisms that result in a supposable deterministic spatial arrangement of mineral, organic, and biotic components. With the growing experimental and observational evidence of the existence and build-up of these sub-micrometer soil compounds, although controversially discussed, the number of modeling approaches increase that aim for an advanced mechanistic understanding of the formation processes, the resulting 3d-structures, and their functions. Research thereby focuses on their role for water storage, biogeochemical cycling of crucial elements including carbon, silicon, iron, or phosphorus, and habitat. With this session, we respond to the growing awareness and intensive debate of the importance of the sub-micrometer-architecture for the functioning of soils. We aim to compile and discuss the concepts and recent advances made in the understanding of formation, composition and functioning of microaggregates in-situ, in-vitro and in silico, as well as the controlling role of the different environments they form in.