The next major stage in microscopy was marked by the development of a radical new instrument: the electron microscope. This was a significant step up in technology, and it made possible exciting new worlds of medical research and practical application. In honoring the pioneers of one of these new developments, cell biology, the 1974 Nobel Prize committee described the electron microscope with a striking analogy: "The difference between this microscope and the ordinary light microscope is enormous, like being able to read a book instead of just the title."33

The electron microscope quickly had an enormous impact on many branches of science, including medicine, following its creation in the 1930s. Researchers could study their particular subjects on an entirely new scale of magnification. For example, electron microscopes made it possible to directly observe viruses for the first time. Also, molecules of DNA, the...