And these light purple cells are the inner cell mass. And this inside and this inner cavity is the blastoceal. It contains that fluid. Now, notice that our blastocyst implants itself along the section of the trophy blast that is adjacent to the inner cell mass. And that's because the inner cell mass needs to be as close to the vascular tissue of the endometrium because it's the inner cell mass that eventually gives rise to that individual, to that organism. Now, as soon as attachment actually takes place, the cells of the trophy blast, these dark purple cells begin to release digestive enzymes.