Placental development is a remarkable morphogenetic process in which fetal trophoblast cells build a functional organ inside the maternal uterus through collective migration, differentiation and invasion. It emerges from a dynamic coupling between fetal and maternal tissues, yet its quantitative biophysics remains comparatively unexplored. At its core lies a three-state problem: trophoblast progenitors can remain proliferative cytotrophoblasts (CTB), differentiate into multinucleated secretory syncytiotrophoblasts (STB), or become migratory, invasive extravillous trophoblasts (EVT). We will ask how this fate choice is controlled not only by the external environment, but also by the microenvironment generated by the trophoblast tissue itself: does the local fraction and spatial organization of CTB, STB and EVT bias the fate of neighbouring cells? We will then place trophoblast organoids in controlled microengineered environments where tissue expansion is mechanically more or less permissive, from free-edge collective migration to 3D gel invasion, where resistance to motion and confinement generate increasing mechanical stresses and pressure. Quantitative live imaging in 2D and 3D will map cell identity, trajectories, flows, density and rearrangements, allowing us to test how tissue composition, neighbour interactions and mechanical resistance jointly control differentiation, migration and invasion.