Organic matter that is insoluble in organic solvents and is preserved within sedimentary rocks. Kerogen is derived from the breakdown and subsequent polymerization of plant and bacterial remains and yields hydrocarbons (oil and gas) on the increase in temperature accompanied by natural burial or laboratory pyrolysis. The chemical and physical characteristics of kerogen are strongly influenced by the type of biogenic molecules from which the kerogen is formed and by diagenetic transformations of those organic molecules.