Abstract: A pioneering process of inducing a photochemical reaction involves upconverted fluorescence from a rare earth ion doped inorganic glass, crystal or other inorganic material. An inorganic host material doped with a rare earth ion capable of upconversion fluorescence is provided. A photoactiveable organic material is positioned at a surface of the inorganic host material, and radiation is directed at the inorganic host material to cause multiple photons to be absorbed by the rare earth ion. A single photon is emitted from the rare earth ion and is absorbed by a chemical species in the photoactivateable organic material to induce a chemical reaction.