Petrology is the study of rocks, and, because most rocks are composed of minerals, petrology is strongly dependent on mineralogy. Petrology studies the composition, texture, and structure of rocks; their occurrence and distribution; and their origin in relation to physicochemical conditions and geologic processes. It is concerned with all three major types of rocks—igneous, metamorphic, and sedimentary. Petrology includes the subdisciplines of experimental petrology and petrography. Experimental petrology involves the laboratory synthesis of rocks for the purpose of ascertaining the physical and chemical conditions under which rock formation occurs. Petrography is the study of rocks in thin section by means of a petrographic microscope.