Changing the scale: slides and electron microscopy at the Virus Laboratory of the Pasteur Institute

Slides are material objects, the daily existence of which cannot be diassociated from the practice of microscopy. But what happens to slides when the examination tool is no longer an optical apparatus but an electon microscope? This is the core issue this paper examines. The answer it proposes is that electron microscope slides are not slides in the classical sense of the word but complex arrangements of materials including plates, cards, photographs and notebooks, which constitute an imaginary "slide," an assemblage the status and existence of which is defined in reference to the heritage of optical microscopy. To illustrate this argument, the paper follows the experimental work of Odile Croissant, the first electron microscopist at the Pasteur Institute in Paris during the 1940s and 1950s when the practices of the new microscopy were introduced and calibrated.