What are some examples of embryogenesis?
I recommend to read Langman's medical embryology books
It is very hard i admit but it is all about human embryology
I am going to explain a little..Zygot as you see is cell and you could define it in 2 dimensions but it is not. As soon as it transforms to blastula they have blastocoel from there the embryonic cells of human was separated into 2 layers the trophoblast and cytothropoblast. and so on..