The document summarizes the process of cleavage in early embryonic development. It describes how the zygote undergoes rapid cell divisions called cleavage to form a solid ball of cells called a morula. The morula then develops a fluid filled cavity called a blastocoel, forming the blastocyst stage. Within the blastocyst, the cells arrange into two layers - an inner cell mass that will become the embryo, and an outer trophoblast layer that will provide nutrition and allow implantation in the uterus.