One often thinks that the early embryo is fragile and needs support. However, at the earliest stages of development, it has the power to feed the future placenta and instructs the uterus so that it can nest. Using ‘blastoids’, in vitro embryo models formed with stem cells, the Lab of Nicolas Rivron at IMBA showed that the earliest molecular signals that induce placental development and prepare the uterus come from the embryo itself. The findings, now published in Cell Stem Cell, could contribute to a better understanding of human fertility.