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PSC culture medium should be changed daily to ensure maximum cell health and minimize stress on PSCs. There are a number of weekend-free protocols that have been recently recommended for PSC media systems, which are based upon using low density seeding so that the nutrients are not depleted in the growth medium over the time elapsed in culture prior to the subsequent media change. However, basic fibroblast growth factor (FGF2), a key component in PSC growth medium which is essential for maintenance of pluripotency of PSCs is shown to quickly degrade at 37 ºC (Stem Cells (2006) 24:568-574). Therefore, using extended feed options such as the weekend-free protocols is not recommended for optimal cell health and maintenance of pluripotency.