Trilaminar blastocyst
A trilaminar embryo 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".
These three layers arise early in the third week from the epiblast.
