Unlike certain materials emitting light through processes such as fluorescence and luminescence, high-quality pigments change the transmission or reflection of light's coloring through the process of absorbing selected wavelengths of light. This process allows the human eye to see the remaining wavelengths as a distinctive color. Pigments are made up of small particles of insoluble materials. Organic pigments — which contain carbon — have been in use for thousands of years and are made from natural materials. Today, however, most organic pigments are synthetic organic pigments made from petrochemical derivatives.