Alejandro Aguilera Castrejon seeks to understand how mammalian embryos develop from a single cell into an animal with specialized organs and tissues, particularly during gastrulation, when patterning of the future body of the embryo begins. Aguilera Castrejon and his team develop platforms and protocols for growing natural and stem cell-derived mouse embryos outside the uterine environment, which they use to investigate normal and perturbed embryogenesis. Studying the mechanisms governing mammalian embryo development will be fundamental for understanding developmental defects, pregnancy loss, and for developing cell and organ replacement therapies.