Vitamin D is a naturally occurring vitamin that is produced by the body in response to sunlight exposure. It was not "invented" by any one person. However, the discovery of the role of sunlight in preventing and treating rickets, a disease caused by vitamin D deficiency, is credited to a number of researchers in the late 19th and early 20th centuries, including Edward Mellanby, Elmer McCollum, and Harry Steenbock. The chemical structure of vitamin D was later determined by Adolf Windaus, for which he was awarded the Nobel Prize in Chemistry in 1928.