1. Extrinsic luminescence approach where a luminophore has been non-covalently grafted or physically doped as a guest within an SCO active materials 2. Intrinsic luminescence approach where a luminescent active ligand is coordinated with SCO center The latter approach has been recommended as an excellent, however challenging way because direct connectivity between the SCO center and luminescent-active ligand allows to control and tune both properties through a structural-property relationship; on the other hand, finding luminescent ligand with appropriate ligand field strength around SCO metal center is more difficult. The resultant complex often becomes luminescence inactive after coordination between the metal center and luminescent-active ligand .