Exploring the ghost world in our genes - the hidden layer of inheritance that lies in every cell of our body. From IVF treatment, to post traumatic stress disorder, to the food our grandparents ate, the controversial science of epigenetics could change the way we think about inheritance forever. At the heart of this new field is the idea that our genes have a memory - that the lives of our grandparents can directly affect us, despite never experiencing these things yourself.