Humipedons correspond to the superficial organic and organo-mineral part of the soil.

All the Earth's crust is covered by humipedons. Exposed to natural evolution, the planet Earth's crust change in time and space. Living beings develop and feed on it in ways related to the quantity and quality of energy that arrives on each point of the globe. Hans Jenny resumed the process of soil formation in a formula: S = f(cl, o, r, p, t, …), where "S" = soil. "cl" = climate, "o" = organisms, "r" = relief such as the topography, “p” = parent material, “t” = time. The humipedon is the first level of an ecosystem formation and it corresponds to a sort of interface between organic and mineral worlds. It is probably in a very liquid humipedon ^[1] that life was born. It can be solid and compact, liquid and very mobile, or very often fixed and lumpy.

To clarify, humipedons have been classified into Terrestrial, Semiterrestrial, Para and Anthropogenic humus systems. Terrestrial systems generate in aerobic conditions (oxidation processes due to aerobic organisms). In the Semiterrestrials' grow the whole range of microorganisms that live in both oxygenated and asphyxiated environments. In the Para there are humipedons generated in other extremely varied environments like bare rocks, walls, accumulations of woody materials, with predominant mosses, lichens or roots, or even more or less acidic hot springs, and lakes/rivers/ocean bottoms. Humipedons in daily tidal and saltwater environments have been classified separately from those not in tidal environments. The anthropized humipedons have been placed in two different boxes: Agro = agricultural, which are used for agriculture; and Techno, made by man, such as manure (composts..) or hydroponic liquid solutions or solid porous clay marbles, but also landfills of different products, including non-organic ones.

Diagnostic horizons have been codified for each humus system ^[2]. Then, depending on the thickness of these horizons, 3-4 forms of humus can be distinguished in each humus system.