Mammals
In mammalian embryogenesis, the columnar cells of the epiblast are adjacent to the trophoblast, while the cuboidal cells of the hypoblast are closer to the blastocoele. The epiblast, whilst referred to as the primary ectoderm, differentiates to form all three layers of the trilaminar germ disc in a process called gastrulation.
Read more about this topic: Epiblast