 Muller’s request did not go unanswered. The next decade saw several famous physicists turn their attention to the nature of inheritance (Keller 1990; Kendrew 1967). In What is Life, the physicist Erwin Schroedinger (1944) proposed ways in which the principles of quantum physics might account for the stability, yet mutability, of the gene (see the entry on  life)  (Elitzur 1995; Moore 1989; Olby 1994; Sarkar 1991; for a reinterpretation see Kay 2000). Max Delbrueck also became interested in the physical basis of heredity after hearing a lecture by his teacher, quantum physicist Niels Bohr (1933), which expounded a principle of complementarity between physics and biology (McKaughan 2005; Roll-Hansen 2000). In contrast to Schroedinger, Bohr (and subsequently Delbrueck) did not seek to reduce biology to physics; instead, the goal was to understand how each discipline complemented the other (Delbrueck 1949; Sloan and Fogel 2011). To investigate the self-reproductive characteristic of life, Delbrueck used bacteriophage, viruses that infect bacteria and then multiply very rapidly. The establishment of “The Phage Group” in the early 1940s by Delbrueck and another physicist-turned-biologist Salvador Luria marked a critical point in the rise of molecular biology (Brock 1990; Cairns et al. 1966; Fischer and Lipson 1988; Fleming 1968; Lewontin 1968; Luria 1984; Morange 1998: Ch. 4; Stent 1968). Delbrueck’s colleague at Cal Tech, Linus Pauling, utilized his knowledge of structural chemistry to study macromolecular structure. Pauling contributed both theoretical work on the nature of chemical bonds and experimental work using x-ray crystallography to discover the physical structure of macromolecular compounds (Pauling 1939, 1970; Olby 1979; Hager 1995; Crick 1996; Sarkar 1998).