A fluorescence microscope instrument includes a light source; an objective focusing light from the light source into a sample and collecting fluorescence light emitted out of the sample; a detector detecting the fluorescence light; and a beam path separator arranged in a first beam path between the light source and the objective and in a second beam path between the objective and the detector. Wavelengths of the light to be directed to the sample and of the fluorescence light to be detected by the detector fall into an extended range of wavelengths. The beam path separator separates the two beam paths in that it is transferable between being transparent for any wavelength of the range of wavelengths and coming along the first beam path, and a second state in which it is transparent for any wavelength of the range of wavelengths and coming along the second beam path.