The increasing concern about visual representation in science has been usually converged on representations – photographs, diagrams, graphs, maps –, while instruments of visualization have been usually neglected, even because of the concrete difficulty to grasp their effects on visualization. In this regard, the questions and concepts formulated in the debate on digital visualization deserve here as a starting point to analyze the change in instrumental mediation triggered by the introduction of computer-assisted imaging technologies in those laboratories that traditionally have (...) used and still use microscopes. Empirical materials gathered during an ethnographic investigation of Italian cytogenetics labs are here presented to show the visual spaces provided by microscopes and digital systems as activity fields, which are inhabited by and suggest in an either divergent or complementary way specific practices, materials, organizations, epistemological orientations and aesthetical preferences. (shrink)