MEM alpha, or Minimal Essential Media with alpha modifications, was first described by Stanners (1971) in culturing mouse-hamster hybrid cells. In addition to Eagle’s MEM, Stanners’ formulation includes non-essential amino acids, ascorbic acid, biotin, vitamin B12, lipoic acid, sodium pyruvate, ribonucleosides and deoxyribonucleosides. MEM alpha has since been used in many applications, such as in maturing human embryos into blastocysts, culturing functional organ tissue in microgravity, and culturing primary cells and cell lines. Commercial formulations of ready-made MEM alpha may come with or without nucleosides.