Serum is the blood component that is obtained after coagulation and removal of cellular components. Besides serum proteins, it contains, e.g. growth factors, amino acids, and hormones. This complex mixture makes serum one of the most important supplements supporting the cells growth and proliferation for in vitro cell culture. Of special interest is the Fetal Bovine Serum (FBS). It is especially rich in growth factors and is particularly low in antibodies that may negatively influence the cell culture work. It supports most cell lines and undergoes strict quality controls. Heat inactivation will inactivate the complement system, antibodies, and other active enzymes. It has to be done in a carefully controlled process to avoid damaging the cell growth-promoting properties of the serum and reducing the formation of unwanted precipitates. The process involves heating the serum in a shaking water bath at exactly +56 °C for 30 minutes. The shaking will help avoid the formation of protein and other forms of precipitates. After 30 minutes the serum is then cooled back down to room temperature as quickly as possible to avoid excessive exposure to heat, which can damage e.g. growth factors and vitamins.