The representation of historical time line of major contributions from scientists who furthered our understanding of photosynthesis.

1. 1643: After analyzing his measurements of a willow tree’s water intake and mass increase, Jan van Helmont concludes that trees gain most of their mass from water.
2. 1771: Joseph Priestley experiments with a bell jar, a candle, and a plant and concludes that the plant releases oxygen.
3. 1779: Jan Ingenhousz finds that aquatic plants produce oxygen bubbles in the light but not in the dark. He concludes that plants need sunlight to produce oxygen.
4. 1845: Julius Robert Mayer proposes that plants convert light energy into chemical energy.
5. 1948: Melvin Calvin traces the chemical path that carbon follows to form glucose. These reactions are also known as the Calvin cycle.
6. 1992: Rudolph Marcus wins the Nobel Prize in chemistry for describing the process by which electrons are transferred from one molecule to another in the electron transport chain.
7. 2004: So Iwata and Jim Barber identify the precise mechanism by which water molecules are split in the process of photosynthesis.