I've seen this question asked in a mature person -- e.g. lip cells will create more lip cells -- but how about in the developing zygote. I've seen neighboring cells help determine the type of the new cell. Do we know how they know where they are located, and how many cells of a certain type have already been made, making "lips" complete, or teeth, etc. So in summary:
1) how do the cells in the growing zygote know "where they are", assuming they need to, to determine what cells to build where for the body?
2) how do the cells know, when the cells of that type building a bone or lips or teeth, etc, are done, since obviously many participate in the process. ?