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How do cells "know" where they are supposed to be in relation to other cells, in forming the physical shape of the body?

If you have ever tried to organise or choreograph the physical positions of a group of people on a field, for example for a dance or display, or even just to stand on stage at a graduation, you will know it takes a bit of communication and working out between the people, and the choreographer (who could be considered a kind of "central intelligence")

Analogy: If you give each person on the field a simple diagram or map (DNA) which shows where the final positions should be, they may or may not be successful, but they would definitely have to talk: "You stand here; I'll be next to you; Jo you need to turn a bit; etc, etc..."

How do cells do this, given than cells could attach and clump in any direction? Especially, how do cells coordinate with other cells quite distant? (Given how small cells are in relation to the shapes & structures of the body)

For example, in my diagram here, 4 cells are forming a specific shape (let's say they're building the corner of an ear or something.) Does cell A "know" where cell C or cell D is?

cells

Please, I'm not after specific chemicals names or in-depth mechanics of cell physiology. I'm after a layman's description or a general principle that is at work.

Bonus related concept: Why/how does the body build a bone of such exact shape the first time around (in the womb) but when you break that bone later, the body seems to just slap bone material around all over, like a bad plasterer?

I've appended a list below of articles I've read (or attempted to read) to try to answer my question.

Stewart
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    I think this might help. – another 'Homo sapien' Jun 09 '16 at 13:06
  • I found this related question after I posted. http://biology.stackexchange.com/questions/21881/how-does-an-embryo-know-where-to-grow-limbs-etc – Stewart Jun 09 '16 at 13:08
  • Does that post answer your question or you have some confusion? – another 'Homo sapien' Jun 09 '16 at 13:15
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    Still reading it ... :) – Stewart Jun 09 '16 at 13:17
  • OK, so I get that my map analogy is flawed. DNA is not a map, it's directions on "how to get there." But still in my diagram, all 4 cells have exact copies of these instructions. How does cell A get to execute different instructions to cell B or C ? – Stewart Jun 09 '16 at 13:25
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    Stewart, read about Hox genes. @another'Homosapien' Quora is an abomination!! :D – WYSIWYG Jun 09 '16 at 13:32
  • Its related to transcription factors. Transcription factors are important to determine which genes are switched on in cell A and switched off in cell B. There is a complex mechanism behind why cell A has transcription factor while cell B doesn't. – another 'Homo sapien' Jun 09 '16 at 13:34
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    @another'Homosapien' Thanks! You've given me a specific terminology which I've never heard of before, which I can look into. That's a very definite starting point! – Stewart Jun 09 '16 at 13:36
  • @WYSIWYG yeah but since there were references in its answer, so I thought it would be useful ;) BTW OP wants layman answer, so hox genes would be a bit difficult to them :P – another 'Homo sapien' Jun 09 '16 at 13:36

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