Fearfully and Wonderfully Made!

I'm starting to get a little fur on top.
I was talking to a friend of mine at Karate a few weeks ago, and her little daughter noticed my eyes looked quite different. I explained to her it was because my eyelashes were gone. I said I was rather looking forward to having them back. Then her mom said, "Oh I don't think eyelashes ever grow back!"
Well, this was alarming!
We're both homeschooling moms, so we decided to make me into a science project - a sort of a unit study on hair growth.
Fortunately, I have since been able to prove her wrong, as I am growing eyelashes and all kinds of facial hair again. In fact, I think my face is a little furrier than it was. I hope the hair on my chin knows when to quit!
This brings us to another interesting question. How do eyelashes know when to quit growing? And other types of facial hair? Isn't it amazing that we grow hair everywhere, and even after some trauma, our hair knows to grow just a little above our eyes, a lot on the top of our heads, and a little on the chin if we're female, but a lot on the chin if we're male. Is this really the result of some big cosmic bang?