Fluorescence refers to the ability of some atoms and molecules to absorb light at a certain wavelength (the excitation: Ex, excitation) and then to emit light of a longer wavelength during a short-lived emission (Em).

Art technology, among others, makes use of this property when examining works of art. Properties can be detected and assigned to specific materials; the spectrum thus becomes material-specific, a kind of optical fingerprint. The storage of such reference spectra in reference databases supports the work of scientists in their research.