Panel 1. With the exception of a few rare «giant» viruses, viruses have a size between 1/80000th to 1/5000th of a millimeter. Only electron microscopy allows for sufficient magnification to observe them. Unlike optical microscopy, where the photons are the elementary particles of light that generate an image, electron microscopy uses electrons. When I started my career, we still used special negative films, sensitive to electrons, which had to be developed in a darkroom to make paper prints. In the early 1990s, cameras detecting electrons replaced these time-consuming methods, allowing for much faster generation of digital-type images.