Nanog is a homeodomain-containing transcription factor that is essential for the maintenance of pluripotency and self renewal in embryonic stem cells. Nanog expression is controlled by a network of factors including Sox2 and the key pluripotency regulator Oct-4. Recent advances in somatic cell reprogramming have utilized viral expression of combinations of transcription factors including nanog, Oct-4, Sox2, KLF4, c-Myc, and LIN28.