The increase in atmospheric carbon dioxide(CO2)concentration is likely to be related to global warming and climate change. Photosynthesis can convert atmospheric CO2 using light and water to produce many kinds of organic molecules. The lack of crystal structures of the enzymes involved in photosynthetic carbon assimilation has hindered the understanding of the detailed mechanisms. Crystallographic studies of the enzymes involved in photosynthetic carbon assimilation provide new insights into the molecular mechanisms.