The Institute of Physico-Chemical Biology: from Foundation to Entrance in the Molecular Era (1927-1960) The Institute of Physico-Chemical Biology (IBPC) was created in 1927, as a joint initiative of Baron Edmond de Rothschild and the physico-chemist Jean Perrin. Their objective was to associate physicists, chemists and biologists within the same building in order to unravel the mysteries of life. Compared to other French institutions, the IBPC was quite original: privately funded, independent of the universities and maintaining close contact with foreign laboratories, the Institute covered a wide range of subjects and benefited from well-equipped workshops that could construct the new physical equipment required for the study of the components of life. In the 1930s, important research was carried out at the IBPC. Using the technique of organ transplantation, George Beadle and Boris Ephrussi studied the developmental and genetic mechanisms responsible for the coloration of Drosophila eyes. This work was seen as one of the first steps toward the construction of the one gene-one enzyme relation. Additionally, experiments using X-ray diffraction to better understand the structure of fibrous proteins were carried out by Emmanuel Faure-Fremiet and Georges Champetier, at the same time as Astbury and Bernal were producing similar data. Finally, Louis Rapkine and Rene Wurmser studied the control mechanisms of the oxydo-reduction potential, its involvement in cell division as well as in Photosynthesis. At the end of the Second World War, the IBPC was still clearly linked to the development of the « new biology », and took an active part in the « Cell Physiology Club » founded by Jacques Monod, which met once a month in the Institute’s library. Together with Piotr Slonimski, Boris Ephrussi began research that was at the origin of mitochondrial genetics. However, the full entry of the IBPC into the molecular era was delayed until the beginning of the 1960s, until the return from the United States of Marianne Grunberg-Manago’s research and the arrival of Francois Gros. There are different possible reasons for this. During the war, the Institute’s activity was quite limited, primarily due to the emigration of many of its key members. In addition, the most highly-developed research at the IBPC – such as the study of Photosynthesis – played only a marginal role in the developments which led to molecular biology. It is striking that microbiology as such never found an important place in the IBPC. The Institute tended to be dominated by a form of physical reductionism that did not favor the development of molecular biology. The scientific leaders at the IBPC were probably also not as charismatic and attractive as Andre Lwoff at the Pasteur Institute.