Are they though? :-) There are some interesting papers in the tissue regeneration space which are working on building tissue (and organs) from stem cells for medical purposes (transplants, injury treatment, Etc.) and one of the things that comes out from that is that a set of stem cells make unique tissue every time in that it's compatible but the fine structure is always randomly different!
While the growth of brain matter is a minefield of ethical issues, at some point I suspect we're going to have to figure out how to do that to treat things like TBI and neurodegenerative diseases. In terms of understanding how randomness plays a part in your existence though cellular biology papers are a pretty good source.