The title, admittedly, is a bit of a stretch – more suited for the biography of some Hollywood femme fatale than a 300-page textbook about the importance of mitochondria. But then Nick Lane makes a persuasive case that we owe these tiny clumps of genetic material lurking in our cells more than we can imagine. It was mitochondria, in his view, that allowed us ‘eukaryotes’ (beings with nuclei in our cells) to break away from the bacteria, to grow larger, to join together, to split into sexes, and now force us to age. This is heavy stuff, but Lane compensates by flattering the reader into feeling that they are being asked to evaluate opinions which other scientists would dub heretical. Challenging, but rewarding.