Humans have always been obsessed with getting old, or rather staying young, and now science is beginning to catch up. Longevity has become a hot topic from university laboratories to Silicon Valley startups. In the second of a special Science Weekly three-part mini-series on ageing, Ian Sample talks to Venki Ramakrishnan, winner of the Nobel prize in chemistry and author of the book Why We Die. Venki outlines the most promising scientific advances in the field of longevity and discusses the more unusual ways that the wealthy are trying to extend their lives, from blood transfusions to cryonics