Medium 199, developed by J.F. Morgan in 1950, was one of the earliest synthetic media developed to grow mammalian cells in culture- in particular, chick embryo fibroblasts. It features a wide array of components including essential and non-essential amino acids, vitamins, salts, glucose, cholesterol, tween, purines, and pyrimidines, among others. Medium 199 was originally designed for chemically defined, animal component-free culturing conditions, making it ideal for virology and vaccine production. In the massive Polio vaccination campaign of 1955, large-scale manufacture of the vaccine was made possible by the discovery of Medium 199.