In 1911 Otto Heimstädt published the description of the first practical fluorescence microscope, developed in the Zeiss environment. The principle differs from bright-field microscopy: instead of observing transmitted or reflected light, the sample is illuminated with high-energy light and the longer-wavelength fluorescent emission is detected. This change in contrast transformed microscopy: instead of seeing shapes, it became possible to make specific molecules, selected structures, or dynamic processes visible. Modern fluorescence microscopy, combined with genetic markers such as GFP (Nobel 2008), is the basis of contemporary cellular and molecular biological imaging.