Have you ever noticed how certain hair on your body grows out to a certain length and then stops while other hair seems to grow indefinitely regardless of how many times you cut it or shave it off? What is that about? Why can’t I get the hair on my face to stop growing? Why does the hair on my arms or chest grow back, but only to a specific length and then stop? Is it possible to rewire these hairs to do what we want them to? Where’s my geneticist?