More than a decade ago, a pathbreaking discovery showed for the first time that mature mouse somatic cells could be reprogrammed into pluripotent stem cells. The discovery was made by using forced expression of four transcription factors Oct4, Sox2, Klf4, and c-Myc. These results came from the research group of Shinya Yamanaka, and hence these factors responsible for reprogramming induced pluripotent stem cells (iPSC) are called the Yamanaka factors [1].