Trilaminar embryo

A trilaminar embryo (or trilaminary blastoderm, or trilaminar germ disk) is an early stage in the development of triploblastic organisms, which include humans and many other animals.

It is an embryo which exists as three different germ layers - the ectoderm, the mesoderm and the endoderm. These layers are arranged on top of each other like a stack of paper, giving rise to the name trilaminar, or "three-layered".

It arises early in the third week, after gastrulation.