When that blastocyst, the embryo actually develop, actually implants itself onto the endometrium, the lining of the uterus. So this is the endometrium, and this is the blastocyst. So recall that the blastocyst consists of a region known as the Trophy Blast. And these are the purple cells, the dark purple cells found as shown. We have the light purple cells that form the inner cell mass. And this entire inner cavity that contains a fluid that provides nutrition to these developing cells is known as the blastocean.