This zygote then undergoes mitotic division, a process that does not result in any significant growth but creates a multicellular cluster called a blastula. This process is referred to as cleavage.

This zygote then undergoes mitotic division, a process that does not result in any significant growth but creates a multicellular cluster called a blastula. This process is referred to as cleavage.

The two cell types -- pluripotent blastula cells (or embryonic stem cells) and neural crest cells -- are both "pluripotent," which means they can become all other cell types in the body.