The research in our group is focused on deciphering a 24h period of mammalian development – the transition from pre- to post-implantation embryogenesis. At E4.5 the mouse blastocyst initiates implantation and transforms into an egg cylinder. This process is characterized with major reorganization in the overall shape, as well as in the transcriptional, epigenetic, and metabolic states of the developing embryo. However, as the maternal tissues engulf and conceal the embryo, the mammalian development at the time of implantation is largely unexplored and probably the most enigmatic period of the early embryogenesis. Using novel biomimetic platforms, we aim to model and dissect the crosstalk between the invading mouse embryo and the maternal environment. At the same time, we want to understand how the developmental program changes gears to shift from pre- to post-implantation embryogenesis, which factors set “points of no return” driving this transition forward and how different pluripotent states define distinct cell shape of the epiblast at blastocyst and egg cylinder stage.