At first glance we only observe the soil surface, but they harbor life inside them and, although it is hidden from our eyes, it plays a fundamental role. It is a world that is largely unknown and invisible. Edaphic microbiology together with enzymatic activity allows us to know about the soil health and nutritional status. Microorganisms can also help to decontaminate soils through bioremediation techniques, which can be coupled with phytotechnologies. The isolation and identification of autochthonous pollutant-degrading microbial consortia allows us to treat contaminated areas using bioaugmentation, natural attenuation, land farming, biopiles or other techniques. Likewise, techniques such as respirometry allow us to evaluate state of the soil. Finally, microbiology is essential to understanding what happens in the digestion of waste or to evaluate the dynamics of pollutants and compounds they form. An unknown world to be discovered.