Humification is the synthesis of stable humic substances in the soil. It is performed with the participation of soil organisms and is part of the decomposition process of plant residues. The formation of humic substances can only take place when the microbial degradation has progressed to such a degree that reactive fission products are present, e.g. monosaccharides, peptides, amino acids or phenolic components. Important starting substances for humification are cellulose and lignin, which belong to the main components of plant cell walls. In particular, lignin has a high resistance to degradation and can be metabolized only by white rot fungi and actinomycetes. Organic basic matter is decomposed and converted into amorphous, high polymer, dark colored humic substances during humification. They are mainly concentrated in the topsoil and have a positive effect on important soil properties such as fertility, aeration and water balance.