On day 38 of #LMB365 we bring you the beginning of life. Early 4-8 cell mouse embryos, as seen under a light microscope, will be left to develop until they form blastocysts. Ross Hill (@rosshill92) will then derive mouse embryonic stem cell (ESC) lines that have the unique potential to form all cell types in an adult organism. In the group of Gerry Crossan in the PNAC Division ESCs are used to study DNA repair in germ cells, the specialised cells responsible for passing on genetic information to the next generation.