Microfauna or microorganisms are organisms that inhabit the soil and are smaller than 0.2 mm. Organisms, which are larger, belong to the mesofauna. Microorganisms, small nematodes and rotifers (wheel animals) belong to the microfauna. They mostly live in a saprophytic way or as bacteria predators in the pores of the soil. Most of the animals in the microfauna can form cysts in unfavorable living conditions and thus survive for several years.