Every time you look in the mirror you see a mystery of biology. Each cell in your body carries exactly the same genetic code, and yet you don’t have teeth growing out of your eyeballs and you never get toenails coming out of your liver. How can one blueprint lead to so many different final structures? Epigenetics. It’s the fastest moving field in modern biology, yet very little has been written on this for a general readership. Now is the perfect time for such a book – not only do we know many examples of epigenetics in action, we’re finally starting to understand the mechanisms of how it works.