SilconOxyCarboNitrides (SiCNO), made from thermal treat-ments of highly cross-linked silicon, nitrogen, and oxygen con-taining polymers, exhibit intense luminescence that is broadly distributed over wavelengths of 500–800 nm. The intensity is sensitive to the composition, and especially to the heat-treatment temperature (T HT) of these new materials. The absorbance in-creases, and thus the brightness of the emission dims, as T HT rises. The phenomenology suggests the presence of two, spatially and energetically separated, molecular complexes: one that ab-sorbs and another that produces photoluminescence. The SiC-NO are an entirely new class of high-temperature materials that can be molecularly tailored for optical device applications.