Organic matter
Soil is composed of minerals and organic matter, as well as living organisms. The organic matter in soil comes from plants and animals. In a forest, for example, leaf litter and woody material falls to the forest floor. This is one kind organic material. When it decays to the point it is no longer recognizable it is called soil organic matter. When the organic matter has broken down into a stable humic substances that resist further decomposition it is called humus.