During fertilization in multicellular organisms, a sperm cell fuses with an egg cell to form a zygote. then, the zygote begins to divide. first, one cell becomes two, then two cells become four, four cells become eight and so on and so forth until a large ball of identical cells is formed. at this point, the ball begins to change. a space forms in the middle, and the cells are pushed inward to form layers. if cell differentiation begins after this phase, what most likely triggers this process?

The process is likely to be triggered by the formation of the layers. Zygote is the structure that forms when a sperm fertilizes an egg, the zygote then divides many times by the process of mitosis to form an embryo. That is, it forms two cells, then four, then eight and so on, up to the eight stage the cells are identical and are called embryonic stem cell, which then develop into any specialized cells type by differentiation, that the growing embryo needs, such as the nerve cells, blood cells, among others.