The main product of the light-dependent reactions of photosynthesis is ATP (adenosine triphosphate) and NADPH. These reactions occur within the thylakoid membranes of chloroplasts and are initiated by the absorption of light energy by chlorophyll. This energy breaks down water molecules, releasing oxygen and generating ATP through chemiosmosis, as well as reducing NADP+ to NADPH. The ATP and NADPH produced are then utilized in the Calvin cycle to convert carbon dioxide into glucose. Overall, these light-dependent reactions are essential for sustaining life on Earth by providing energy and organic materials.