Fetal bovine serum (FBS) has been used extensively as a supplement in cell culture media since the mid-20th century. In the late 1940s and 1950s, scientists working to develop techniques for culturing animal cells discovered that serum obtained from blood collected from fetal calves supported cell growth better than adult bovine serum or serum from other species. https://timessquarereporter.com/others/fetal-bovine-serum--essential-for-cell-growth-but-raising-ethical-concerns