The layer of tissue that forms the wall of the blastocyst in the early stages of embryonic development. The trophoblast helps to implant the blastocyst to the uterine wall and supplies nutrients to the embryo. During implantation, the trophoblast differentiates into two layers. The inner layer, the cytotrophoblast forms into the chorion. The outer layer, syncytiotrophoblast, develops into the outer layer of the placenta. The trophoblast is also known as the trophectoderm.