The remains of plant or animal life found in ancient geological strata are called fossils. This evidence of life can reach the state fossil by the petrification, carbonization and impressions. The petrification is the process by which the porous parts of the bones of vertebrates buried for millions of years are filled with minerals or directly are transformed into minerals, which can maintain the cell structure of original living organism. Some agencies, such as mosses and insects, were preserved because they were covered with pine resin. The carbonization is another process of fossilization, which is recorded mainly in plants. When they fall into the water, eventually are covered with sediments, lose some elements of its composition and structure is mainly composed of carbon. The impressions are the impressions or molds that are leaving some living without retain any part of their tissues, as with fossil shells. In the prints found, from footprints of animals found to leaf mold, rodent burrows.
The science that studies fossils is called paleontology and classified into three branches: paleobotany, paleontology of invertebrates and vertebrate paleontology.
The Agricultural mineralogist, of German origin, wrote in 1541 De natura Fossilium, a treatise on fossils in which minerals mainly investigated. Later the term was used only for organic waste.