Despite the huge place molecular biology has acquired in biological research, it remains difficult to provide a definition of it. Is molecular biology a scientific discipline, or a new vision of organisms? When did it emerge? Is molecular biology still alive, or has this discipline died, and been replaced by new disciplines such as systems and synthetic biology? Were molecular biologists too reductionist?

Three successive steps can be distinguished in the history of molecular biology: the 1930s, with the development of new technologies aimed at describing the structure of macromolecules, and an effort to ‘naturalize life’; a relatively short period (1940–1965) in which the main results were obtained; and the huge accumulation of molecular data that has modified biology since this time. Despite the fact that molecular explanations have in part reached their limits, I consider that molecular biology has succeeded in ‘naturalizing life’.

Key concepts:

Reductionism, to naturalize a phenomenon, systems biology, synthetic biology, mechanistic explanations, relations between molecular and evolutionary biology.