 Molecular biology’s classical period began in 1953, with James Watson and Francis Crick’s discovery of the double helical structure of DNA (Watson and Crick 1953a,b). Watson and Crick’s scientific relationship unified the various disciplinary approaches discussed above: Watson, a student of Luria and the phage group, recognized the need to utilize crystallography to elucidate the structure of DNA; Crick, a physicist enticed by Schroedinger’s What is Life? to turn to biology, became trained in, and contributed to the theory of, x-ray crystallography. At Cambridge University, Watson and Crick found that they shared an interest in genes and the structure of DNA (see the entry on  scientific revolutions).