It drives the embryo proper through its differentiation into the three primary germ layers, ectoderm, mesoderm and endoderm, during gastrulation.

[2] Other early embryologists that studied the epiblast and blastoderm include Karl Ernst von Baer (1792-1876) and Wilhelm His (1831-1904).

[4] This specification is accompanied by extensive epigenetic reprogramming that involves global DNA demethylation, chromatin reorganization and imprint erasure leading to totipotency.

[5] Upon commencement of gastrulation, the primitive streak, a visible, morphological linear band of cells, appears on the posterior epiblast and orients along the anterior-posterior embryo axis.

The first wave of epiblast cells to invaginate through the primitive streak invades and displaces the hypoblast to become the embryonic endoderm.

The process of gastrulation results in a trilaminar germ disc, consisting of the ectoderm, mesoderm and endoderm layers.

A local thickening of the epiblast, known as Koller's sickle, is key in inducing the primitive streak, the structure through which gastrulation occurs.

[10] Ancestors of Amniotes (mammals, birds, reptiles) underwent gastrulation primarily by an infolding of the epiblast layer (involution).