The present review on light emission stimulated by electrons tunneling inelastically through a junction formed by a sample and a tip of a scanning tunneling microscope (STM) focusses on the most relevant results obtained for a variety of systems, including metal surfaces, single molecules on ultrathin dielectric films, and molecules assembled in thin films or in nanostructures on metal surfaces or on dielectric films. The decisive role of the localized surface plasmon for the enhanced luminescence from supported molecules is highlighted. The progress so far achieved for both experimental techniques and theoretical analysis is addressed. Current trends are discussed and possible future developments are indicated. STM-induced photon emission has come a long way. More than a decade ago, simple photon maps reflected only the emitted light intensity on a local scale. Today this technique has advanced to spectroscopically resolve optical emission from electronic and vibrational molecular modes in single molecules, demonstrating the capability of STM-induced light emission for chemical recognition on the single-molecule scale. © 2010 Elsevier B.V. All rights reserved.