Photosynthesis must feel immediate, not abstract. In a sunlit corner we build a simple oxygen-collection rig: a leaf submerged under a funnel with a graduated pipette at the stem collects gas bubbles, tiny trophies of carbon fixation. We change light intensity with cardboard shutters and note how production rises and falls. Someone asks about chlorophyll fluorescence; I hand over a portable fluorometer and we watch a leaf’s stress readout spike after a minute under a heat lamp. Graphs born from their own hands — curves of light response, saturation points — suddenly matter because they’re not lines on a page, they’re fingerprints of life.