Leaves are green because they have photosynthetic pigments. Therefore, leaves are able to assimilate light (solar light). Also, leaves are able to "breath" CO2. Both features, solar light assimilation and CO2 intake, allow leaves to produce sugars. These require at least two great types of molecules in leaves, the first one, i) structures and molecules to assimilate, use and manage solar radiation and its derived damage, and the second one ii) enzymes able to use this energy and environmental CO2 to build sugars.