Williams’ Medium E was developed by G. M. Williams and J. M. Gunn in 1974 in culturing a high viability population of epithelial cells from adult rat livers. The original formulation included all 20 amino acids, ascorbic acid, biotin, calcium panthothenate, choline chloride, disodium alpha-tocopherol phosphate, ergocalciferol, folic acid, glutathione, inositol, menadione sodium bisulfite, methyl linoleate, nicotinamide, pyridoxal, riboflavin, pyruvate, thiamine, vitamin A, vitamin B12, glucose, salts, phenol red, and supplemented by 10% fetal bovine serum. Commercial formulations of Williams’ Medium may contain alternative components or supplements.