On page 1191, Tyagi et al. describe “wavelength-shifting molecular beacons,” a technology that expands the number of molecular beacons that can be used to detect different complementary nucleic acid targets simultaneously. Molecular beacons are hairpin-shaped nucleic acids with a fluorophore and a nonfluorescent quencher attached to either end. When the hairpin is closed, fluorescence is quenched, but upon annealing to a complementary sequence the molecule becomes linear and fluorescence is restored. The researchers set out to develop a series of fluorophores that could be stimulated by the same monochromatic light, but could be distinguished from one another by the different wavelengths of light they emit. In addition to the quencher and emitter fluorophores, the modified molecular beacons contained an additional “harvester” fluorophore that absorbs monochromatic light, and when the beacon is bound to a target, transfers energy to the emitter fluorophore. This shifts the emission spectrum of the emitter by fluorescence energy transfer so that each fluoresces in its own characteristic color.