Green plants, algae and some bacteria use sunlight to convert energy. The pigments in chlorophyll absorb electromagnetic radiation, which induces chemical reactions in electrons. These reactions take place in the nucleus of complex protein structures, referred to by experts as photosystems I and II. The processes that take place in these photosystems are induced by catalysts in a certain order. In the first step, oxygen is released from water. A subsequent reaction prepares the production of carbohydrates for which no further source of energy is needed.