Pathophysiology, also called physiopathology, is the convergence of the fields of physiology and pathology. This field attempts to explain the physiological processes and/or mechanisms whereby such pathological conditions develop and progress. It can also mean the functional changes associated with or resulting from disease or injury to the body. Studied since the late 19th century, this field has benefited from the plethora of research improvements that have made it possible to investigate disease processes all the way to the molecular level. Throughout the roughly 150 years that pathophysiology has been studied it has both created and benefited from many specialized branches of medicine; cytology, experimental pathology, bacteriology and germ theory, molecular genetics, biochemistry, and chromosomal genetics, all of which have culminated in the many uses of DNA.