Publisher Summary When the first electron microscopes became available to biologists, a long tradition in the domain of cytology already existed in France. The event presented a unique opportunity to end many discussions, often fiery, that divided scientists on the structure and significance of certain cell organelles. In the beginning, only a few laboratories were equipped. Many of the contributions from these laboratories represent first discoveries or descriptions, and they are important landmarks in the history of cell ultrastructure. This chapter reports some of the early findings. W. Bernhard presented a summary of the findings on the ultrastructure of viruses in Columbus (Ohio) at the XVIIth meeting of the European Medical Students' Association (EMSA). The advances, the detailed morphological, and beautiful images of viruses, that of the adoption by the international community of the ultrastructural description and denomination proposed by Bernhard and the Villejuif group for the now-called retroviruses, set France in the forefront of the domains of electron microscopy and viruses.