Over the last century, we have gone from ignorance as to why some diseases run in families to the availability of simple genetic tests that can be bought on the internet. And from announcements of the death of Darwinism to the triumph of the modern theory of evolution. All this is thanks to the fruit fly, the guinea pig, the zebra fish and a handful of other organisms, which have helped us unravel one of life's greatest mysteries - inheritance. Jim Endersby's strikingly original book tells the history of modern biology through the stories of the animals and plants that made it possible, showing how the guinea-pig and its colleagues have played a pivotal role in our gradual understanding of what genes are and what they do. By spending years laboriously breeding these animals and plants, observing the consequences and extrapolating - sometimes quite wildly - from these observations, scientists have gradually come to understand how inheritance shapes generations to come. In telling their stories, Endersby reveals the development of perhaps the most significant science of our times. Endersby traces his story from Darwin hand-pollinating passion flowers in his back-garden in an effort to find out whether his decision to marry his cousin had harmed their children, to today's high-tech laboratories, full of shoals of shimmering zebra fish, whose bodies are transparent until they are mature, allowing scientists to watch every step as a single fertilised cell multiplies to become the millions of specialised cells that make up a new fish. Each story has - piece by piece - revealed how DNA determines the characteristics of the adult organism. Not every organism was as cooperative as the fruit fly or zebra fish, some provided scientists with misleading answers or encouraged them to ask the wrong questions. Entertaining, surprising and enlightening by turns, this unusual and original view of the science of life also challenges us to consider the ethical dilemmas that biology presents today - when we have the capacity as never before to change the very nature of living things.