Energy is the most important issue of the 21st century. Due to severe environmental problems, mainly related to air pollution of urban areas and green house effects leading to global warming, fossil fuels need to be replaced by renewable energy sources. Beside the wind energy, which is progressively more and more exploited, solar energy represents a clean, abundant, diffuse and economical energy which can be converted into heat, electricity or in the form of so called solar fuels, provided special materials are developed able to efficiently absorb solar light and produce charge separation. This is the prerequisite for obtaining electricity from sunlight and solar fuels, e.g. hydrogen from water photosplitting or carbon containing species from carbon dioxide photoinduced reduction, which can be stored and used on need. Converting solar energy into chemical energy is thus a big challenge for chemistry.