Cardiomyocyte Selective Medium Growth Supplement (CSGS) is a medium supplement designed for the selective growth of pluripotent stem cell derived cardiomyocytes in vitro. It is a sterile, concentrated (50X) solution which contains growth factors, hormones, and proteins. The supplement is formulated (quantitatively and qualitatively) to provide an optimally balanced growth environment that promotes the growth of cardiomyocytes, but not other cell types. CSGS is designed as an additive for Cardiomyocyte Selective Medium (CSM, Cat. #5911) and should be used in conjunction with that medium