Moshe Szyf is a pioneer in the field of epigenetics, the study of how living things reprogram their genome in response to social factors like stress and lack of food. His research suggests that biochemical signals passed from mothers to offspring tell the child what kind of world they're going to live in, changing the expression of genes. "DNA isn't just a sequence of letters; it's not just a script." Szyf says. "DNA is a dynamic movie in which our experiences are being written."