Subject: How do cells 'know' how to form a blastula?

I would imagine it is similar to the formation and movement of a "slug" from
slime mold (with the release of hormones/cAMP after a trigger).  I am confused
as to how the cells know when to form a "bubble" and how to structure themselves
in relation to each other.  On top of that, how do they trigger themselves to
form a cup/cavity?  Is the organized communication hormone related? Also, what
is the study of this called and is there a journal or other resource that has
plenty of information and is up to date.  Just to clarify I am talking about a
human/animal blastula.

Re: How do cells 'know' how to form a blastula?