We have the blastoceal, which is the hollow cavity inside the blastocyst that contains a nutritious fluid that is needed by that developing embryo to actually develop further. We also have a structure known as the trophy blast and the inner cell mass. Now, the cells part of the trophy blast eventually give rise to a structure known as the corian, as well as the placenta, while the cells of the inner cell mass eventually give rise to the actual organism itself. Now, following the formation of the blastocyst, the blastocyst finds itself inside the fluid found inside the cavity of the uterus. What exactly happens next? Well, for the blastocyst to develop further, it must actually implant itself onto the endometrium, the lining of the uterus.