Soil fauna are functionally important in many ecosystems. They represent large variety of organisms of different sizes and life strategies that may affect soil processes on many different spatiotemporal scales. Small members of soil fauna such as nematodes or protist are important predators of soil microflora and may affect nutrient dynamic in micro sites such as rhizosphere, larger body soil fauna fragment litter and transform it into fecal pellets that form an important part of the soil profile, mix organic and mineral layers, create soil aggregates, burrows and other microstructures in soil. Soil fauna substantially modulate microbial activity either by selective predation and or by creation of specific microhabitats. Soil fauna is ‘‘the real conductors of microbial symphonies’’ which tune microbial activities in complex multi-scale interactions. These fauna activity substantially affect soil hydrology, nutrient dynamic, soil formation, plant soil interaction and many other key soil processes. All aspect of soil fauna interaction with key soil processes including but not limited to physical environment of soil, soil microbial activity nutrient dynamic, and plant soil interactions will be considered in this section.