.....We now show that hypoxia can govern cell fate decision since hypoxia alone can revert hESC- or iPSC-derived differentiated cells back to a stem cell-like state, as evidenced by re-activation of an Oct4-promoter reporter. Hypoxia-induced "de-differentiated" cells also mimic hESCs in their morphology, long-term self-renewal capacity, genome wide mRNA and miRNA profiles, Oct4 promoter methylation state, cell surface markers TRA1-60 and SSEA4 expression and capacity to form teratomas. These data demonstrate that hypoxia can influence cell fate decisions and could elucidate hypoxic niche function.