Dorothy Hodgkins model of pig insulin, c 1967.

UNITED KINGDOM - MARCH 06: Insulin is a protein hormone produced in the pancreas, which regulates the metabolism of glucose, fats and proteins. It was discovered in 1921 by the Canadian physician Frederick Banting (1891-1941), who pioneered the use of insulin for the treatment of diabetes. Insulin was the first protein to have its molecular structure completely established, by X-ray crystallographer Dorothy Crowfoot Hodgkin (1910-1994) in 1969. This model of pig insulin clearly shows the complexity of its molecular structure. (Photo by SSPL/Getty Images)