Fetal Bovine Serum (FBS) is a time tested, universal supplement used in cell culture. It provides many compounds that have been shown to satisfy specific metabolic requirements for the culture of cells, including hormones, growth factors, cell attachment factors, pH buffer, protease inhibitors, vitamins, minerals, lipids, and a variety of undefined components. Serum also protects against toxic effects associated with pH change, the presence of heavy metal ions, endotoxin, and proteolytic activity.