Fetal bovine serum (FBS) is derived 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. The globular protein, bovine serum albumin (BSA), is a major component of fetal bovine serum. The rich variety of proteins in fetal bovine serum maintains cultured cells in a medium in which they can survive, grow, and divide. Because it is a biological product, FBS is not a fully defined media component, and as such varies in composition between batches. As a result of this and in an attempt to minimize the possibility of transfer of adventitious agents, serum-free and chemically defined media (CDM) have been developed. The effectiveness of serum-free media is limited, however as many cell lines still require serum in order to grow, and many serum-free media formulations can only support the growth of narrowly-defined types of cells. Production FBS is a by-product of the meat industry. FBS, as with the vast majority of animal serum used in cell culture, is produced from blood collected at commercial slaughterhouses from cattle that also supply meat intended for human consumption. The first stage of the production process for FBS is the harvesting of blood from the bovine fetus after the fetus is removed from the slaughtered cow. The blood is collected aseptically into a sterile container or blood bag and then allowed to clot. The normal method of collection is cardiac puncture, wherein a needle is inserted into the heart. This minimizes the danger of serum contamination with micro-organisms from the fetus itself, and the environment. It is then centrifuged to remove the fibrin clot and the remaining blood cells from the clear yellow (straw) colored serum. The serum is frozen prior to further processing that is necessary to make it suitable for cell culture. The second stage of processing involves filtration, typically using a filtration chain with the final filtration being three sterile 0.1 micron membrane filters. The aseptically processed FBS is subjected to stringent quality control testing and is supplied with a detailed Certificate of Analysis. The certificate gives full test results and information concerning the origin of the serum.