And that hole is eventually sealed off by blood clots, as well as by developing epithelial cells. So, in diagram two, the entire embryo is found inside that endometrium. And also notice that the cells of the inner cell mass differentiate into two different types of cells. We have the green cells that make up the hypoblast, and we have these blue cells that make up the epiblast. Now, the hypoblast cells eventually give rise to the endoderm, while the epiblast eventually gives rise to the ectoderm. And as we'll see in just a moment, the mesoderm develops in between as a result of a process called invagination, when we form that primitive treat, as we'll see in just a moment.