RPMI 1640 medium was developed by Moore and his co-workers while at Roswell Park Memorial Institure in 1966. Originally designed for the growth of human leukaemia cells in monolayer or suspension cultures using a serum supplement, it has since demonstrated universal use in the growth and support of a broad spectrum of mammalian and hybrid cells as well as in hybridoma fusion protocols. For peripheral blood lymphocytes a mixture of 80% RPMI 1640 and 20% FBS is often used, and for murine myeloma cells a mixture of 85% RPMI and 1% FBS. Different from the original formulation, only 0.05 mg/l riboflavin are used due to risk of photo oxidative effects.