the blood fraction remaining after the natural coagulation of blood, followed by centrifugation to remove any remaining red blood cells.[1] Fetal bovine serum comes from the blood drawn from a bovine fetus via a closed system of collection at the slaughterhouse. Fetal bovine serum is the most widely used serum-supplement for the in vitro cell culture of eukaryotic cells. This is due to it having a very low level of antibodies and containing more growth factors, allowing for versatility in many different cell culture applications.