Insulin-Transferrin-Selenium-100X (ITS) is a mixture of insulin, transferrin, and sodium selenite, serving as a versatile supplement designed for use with classical media such as DMEM and RPMI-1640, as well as nutrient media like Ham's F-12 and DMEM/F-12. This supplement is added to basal media to reduce the amount of fetal bovine serum required for cell culture.