It is very important to know in advance the optical properties of all the constituents in the spectral region to develop a final product. These properties are needed to the develop final products for spectrally selective surfaces, for photo-, thermal- and photovoltaic energy conversion, as well as for the radiative cooling surfaces, disguise surfaces, smart sensors, smart windows, etc. The number of possibilities for engineering coatings to meet specific demand of application is more or less unlimited. Qualitative control and long durability of products is possible only by knowing the connections between optical, electrical and structural properties of materials used. Research carried out within the program is technologically very important for the following research and development of different areas in Slovenia. 1. Development of new energy sources. 2. Paint industry (pigments, coatings, resins, etc.). 3. Critical technology (semicondutors, smart sensors, detectors, production of surface microstructures). 4. Ecology.