Fluorescence is a phenomenon in which illuminated materials emit light of a different wavelength to the incident light. Fluorescence microscopes create an image from the distribution of this emitted light from a sample, as opposed to transmitted or reflected light. The characteristic wavelength of the fluorescent light can be used to identify specific fluorophores (fluorescent chemicals) present in the sample.
Fluorescence microscopy was originally developed for use in the life sciences, but it is increasingly finding applications in materials science. Today, fluorescence capabilities are commonly found on compound microscopes and metallographs, for stereomicroscopes, and in vision engineering systems.