Human embryonic stem cells (ESCs0offer considerable promise for curing a range of intractable diseases and injuries which constitute a significant health burden costing billions of dollars globally. However it is now generally accepted that human ESCs cells are not the same as those originally isolated in mice (naïve ESCs) but more like mouse epiblast stem cells (primed ESCs). While both cell types share some features they differ in that primed mouse ESCs do not produce chimaeric animals which remains the “gold standard” in terms of demonstrating pluripotency. This has been interpreted to mean that existing human ESC lines are not as pluripotent as those originally isolated in mice. Naïve ESCs have recently been isolated and shown to have a number of advantages compared with primed cells including greater proliferative capacity, karyotype stability and differentiation potential lending further support to this suggestion. We have developed a new method for isolating ESCs which differs from those originally developed for naïve ESCs in that that these are isolated earlier in development from the inner cell mass prior to its differentiation. This ESC type has been characterised extensively and shown to be more like naive ESCs than primed cells. While our cells are closer to naïve than primed ESCs they nevertheless represent a new cell type because they are isolated earlier in embryo development. As such we believe these may have added advantages in terms of their cell therapy potential.