Nanog protein is a key transcription factor crucial for maintaining pluripotency in mammalian early embryos and pluripotent stem cells. It contains a homeodomain and is involved in various cellular processes, including self-renewal and reprogramming. Nanog is essential for the acquisition of pluripotency and the reactivation of the X chromosome, playing a central role in the transcriptional network of pluripotency. It forms autoregulatory loops to maintain embryonic stem cell (ESC) identity and is indispensable for the transition to full pluripotency during reprogramming. Nanog's expression is complex and regulated at multiple levels, and it is associated with diseases such as teratocarcinoma and germ cell and embryonal cancer. Additionally, Nanog has been implicated in cancer progression, acting as a cancer stem cell marker and promoting the self-renewal and long-term proliferative potential of stem cells.