The formation of a human embryo starts with the fertilization of the oocyte by the sperm cell. This yields the zygote, the primordial cell that carries one copy each of the maternal and paternal genomes. However, this genetic information starts being expressed only after the zygote divides a couple of times. But what triggers this process, called “zygotic genome activation”, was unknown until now. EPFL scientists have just found that members of the DUX family of proteins are responsible for igniting the gene expression program of the nascent embryo. Published in Nature Genetics, this discovery is a milestone for developmental biology.