What happens after fertilization?

Fertilization results in the creation of a zygote. The zygote begins the process of cleavage or cellular replication, resulting in a morula or ball of cells. At 3 days post-conception a solid ball of 16 cells is present. This blastomere begins to separate into two parts: the trophoblast or outer layer of cells, which will form the placenta, and an inner cell mass or embryoblast, which will begin to differentiate and evolve into the embryo, and a cavity forms within the cell mass. When the cavity is recognizable, the structure of the developing embryo is called a blastocyst. The blastocyst will then implant into the endometrium lining.