When modern microscopy was still in its infancy in the 1870s, a German physicist and microscope manufacturer named Ernst Abbe stated that optical microscopes would never be capable of showing something smaller than 0.2 micrometers in size. He calculated this limit based on how small a glass lens could be built that still focused the wavelength of visible light. That’s small enough to let us see really tiny things, such as the main structures inside animal cells like mitochondria, but not small enough for us to see DNA and proteins.
While Abbe’s calculations were accurate, his prediction was not. More than a century later the 2014 Nobel Prize in Chemistry has been awarded to the men who proved Abbe wrong. Eric Betzig, Stefan W. Hell, and William E. Moerner sidestepped the limitations of traditional optics by looking at molecules using light the molecules produce themselves. The simple version is that they can control which molecules glow to obtain a higher-resolution image than they would get if everything was glowing at the same time.
The importance of this discovery might seem insignificant compared to electron microscopy, which can show objects smaller than 50 picometers (one trillionth of a meter). Electron microscopes shoot beams of concentrated electrons at their subjects that, when combined with colored dyes to get the necessary contrast, often end up damaging them. Optical microscopy offers scientists a relatively unobtrusive method of observation.
Long before any of these Nobel Prize–winning scientists did their work, and 200 years before Abbe proclaimed to be impossible what the winners succeeded in doing, Antonie van Leeuwenhoek saw microorganisms under a microscope of his own making. His work, and that of later microbe hunters, was dramatically retold in Paul de Kruif’s book Microbe Hunters. You can read about the impact of de Kruif’s book on the scientific world in the upcoming issue of the magazine.
By Jacob Roberts
Image: Illustration of spermatozoa by Antoine van Leeuwenhoek, published in Opera omnia, seu arcana naturae (1722–1730). The cells probably came from a rabbit. Wellcome Images.