Negative staining of viruses, arguably the technically simplest and most important single method in virology, was introduced in 1956. Hall and later Brenner and Horne used phosphotungstic acid for contrasting plant viruses. 8, 12 This technique was extended in 1959 to coliphage T2. 9 Viruses and their components stood out as white on a dark background with unprecedented clarity. Negative staining by phosphotungstates rapidly superseeded shadowing for virus visualization. Uranyl salts and ammonium molybdate were introduced later. The standards of viral electron microscopy were set in the 1970s. 11, 20, 21 Today, negative staining is done almost exclusively with uranyl acetate (UA) and phosphotungstate (PT) salts (Figs. 1 and 2) and has been applied to thousands of viruses. At present, at least 6,300 bacterial and archaeal viruses have been examined in the electron microscope after negative staining. 6 Transmission electron microsocpes (TEMs) fall into three categories. (1) Conventional or "manual," also called "analogue" microscopes using mechanical devices for stage drive and aperture alignment and analog potentiometers or variable resistors for electronic controls. Images are recorded on photographic film or plates. (2) "Digital" microscopes using far fewer controls due to a computer-based system with digital potentiometers, electronic stage drives, and a digital alignment via a centralized computer interface. Objects are generally visualized on a monitor screen and images are acquired via a "chargedcouple device" or CCD sensor, replacing film or plates as the recording media.