Illustration of the US physicist Eric Betzig (born 1960). Betzig is best known for his work to increase the resolution limit of optical microscopy. His PhD and post-doctoral work was on near-field microscopy. The resolution of optical microscopes is limited by the size of the smallest wavelength of visible light (between 200-300 nanometres). Near-field microscopy was able to exceed this limit by focusing the light through an aperture smaller than its wavelength. However, it cannot probe the specimen at any depth and cannot be used to study living cells. Betzig had the idea to use fluorescent proteins that could be turned on and off to tag a specimen. Taking multiple images with different proteins fluorescing each time and then combining the images gave a super-resolution image and could be used to image living cells. Betzig won a share of the 2014 Nobel Proze in Chemsitry for this work with Stefan W. Hell and William E. Moerner.