This paper is about the interaction and the intertwinement between history of science as a historical process and history of science as the historiography of this process, taking molecular biology as an example. In the first part, two historical shifts are briefly characterized that appear to have punctuated the emergence of molecular biology between the 1930s and the 1980s, one connected to a new generation of analytical apparatus, the other to properly molecular tools. The second part concentrates on the historiography (...) of this development. Basically, it distinguishes three phases. The first phase was largely dominated by accounts of the actors themselves. The second coincided with the general ‘practical turn’ in history of science at large, and today’s historical appropriations of the molecularization of the life sciences appear to be marked by the changing disciplinary status of the science under review. In a closing remark, an argument is made for differentiating between long-range, middle-range and short-range perspectives in dealing with the history of the sciences. (shrink)