The process of cell division, known as mitosis, begins when the zygote travels toward the uterus. During this movement, it divides repeatedly to form 2, 4, 8, and 16 cells called blastomeres. This cluster of cells develops into the first embryonic stage known as the morula.
As the morula continues dividing and moves further into the uterus, it changes into a blastocyst. In the blastocyst, the blastomeres arrange themselves into an outer layer called the trophoblast and an inner group of cells known as the inner cell mass. The trophoblast later attaches to the endometrium, while the inner cell mass develops into the embryo.
After attachment, the cells of the uterus multiply rapidly and surround the blastocyst. The blastocyst then becomes embedded in the uterine lining, a process known as implantation.
