All of our food comes either directly or indirectly from photosynthesis of CO2 and H2O. The energy released by oxidation of a simple sugar molecule (C6H12O6) is about 29 electron volts (eV). The only way we can produce sugar from CO2 and H2O is through photosynthesis in chloroplast. But visible light photons are only about 2 to 3 eV. How many sunlight photons are required to produce a C6H12O6 molecule? Is there any way we can improve on the Calvin cycle (or C4 cycle) for our food production?