A blastomere is a type of cell produced by division of the egg after fertilization. Human blastomere In humans, blastomere formation begins immediately following fertilization and continues through the first week of embryonic development. About 30 hours after fertilization, the egg divides into two cells. These mitotic divisions continue and result in a grouping of cells called blastomeres. During this process, the total size of the embryo (also called a "zygote") doesn't increase, so each divis… (More on Blastomere)