Pluripotent mouse embryonic stem (ES) cells are obtained directly from the mouse epiblast, while pluripotent embryonic germ (EG) cells can be derived from unipotent mouse primordial germ cells (PGCs) by epigenetic reprogramming. But how similar are EG and ES cells? On p. 2279, Azim Surani, Austin Smith and colleagues report that these cells share a conserved molecular and developmental ‘ground state’. ES cells can be established using the cytokine LIF combined with the inhibition of GSK3 and of mitogen-activated protein kinase signalling (so-called 2i-LIF culture). The researchers show that pluripotent mouse EG cells can also be efficiently established using 2i-LIF culture. Then, using the same conditions, they derive rat EG cells for the first time. These cells express similar markers to rat and mouse ES cells, they report, and can contribute extensively to chimeric rats. Together, these findings raise the possibility that 2i-LIF culture could be used to derive EG cell lines with pluripotent ground state properties from other species, including humans.