A series of reactions that occur during photosynthesis in the inner area, or stroma, of chloroplasts, aka the photosynthetic organelle in plants. The Calvin cycle is part of the light-independent reactions of photosynthesis. During the Calvin cycle, carbon dioxide (CO2) is “fixed” using energy in the form of adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide phosphate (NADPH), which are generated in the first stage of photosynthesis, called the light-dependent reactions.