Now, once it reaches the cavity of the uterus it undergoes a process known as blastulation to form a blastocyst. And about seven days after fertilization took place that blastocyst will implant itself onto the endometrium onto the lining of the uterus of that individual woman. And once implantation takes place, we begin to form the placenta. Remember, the placenta is the organ that eventually begins the exchange of nutrients and gases between the mother and that fetus. Now, once implantation takes place, we also begin the process of gastrelation. Now remember, gastrolation is the process by which we form the three different germ layers.