Crick and Watson's discovery of the structure of DNA fifty years ago marked one of the great turning points in the history of science. Biology, immunology, medicine and genetics have all been radically transformed in the succeeding half-century, and the double helix has become an icon of our times. This fascinating exploration of a scientific phenomenon provides a lucid and engaging account of the background and context for the discovery, its significance and afterlife, while a series of essays by leading scientists, historians and commentators offers uniquely individual perspectives on DNA and its impact on modern science and society.