Historians of science have long agreed that the turn of the 17th century was marked by a "decline of microscopy". This view is now being challenged by a number of studies (Generali and Ratcliff 2007, Schickore 2007). This term was used by a community of historians of science to refer to the fact that by the end of the seventeenth century, the microscopic research activity that had been carried out since 1660 by scholars, especially Dutch, English and Italian, had weakened to such an extent that by the beginning of the eighteenth century, with the exception of the Dutch scientist Antoni van Leeuwenhoek, it was practically non-existent. In contrast to this approach, the present work compares the use of the microscope in the two most prominent learned societies of the early eighteenth century, the Royal Society and the Académie des sciences de Paris. From a historiographical point of view, the "decline of microscopy" can only be seen as the result of a systematic lack of serious research. From a historical point of view, the data presented here allow us to envisage a completely different line of interpretation for this decline, partly sociological, partly linked to the scientific controversies at the turn of the 17th century and the transformation of the microscope's status as a routine instrument at the beginning of the Enlightenment.