The second stage of photosynthesis is called the dark stage. It is the part of the process when carbon dioxide is stored as sugar in the plant.
The dark reactions are so called because they can take place in the absence of light, whereas the light reaction stage of photosynthesis, also its first stage, requires light.
Carbon fixation is another name for the process that takes place during the conversion of carbon dioxide to sugar. Also called the Calvin cycle, after its discoverer, it involves three steps or sub-stages of chemical reaction as the plant produces its food from carbon dioxide, including carbon fixation, reduction and regeneration.