Nitronyl nitroxides are stable free radicals that have been used to prepare new molecular solids with intriguing magnetic properties. These properties have been probed for the electronic ground state using a large number of different physical techniques and theoretical methods. In contrast, the excited states and optical spectroscopy of these compounds and their metal complexes have received little attention until recently. In this overview, we present their absorption and luminescence spectra. Luminescence is observed between 700 nm and 1100 nm, and the lowest-energy absorption bands occur between 500 nm and 700 nm. Several excited electronic states are in the red to near-infrared wavelength range, leading to a wide variety of interesting spectroscopic features.