The document discusses the light-independent reactions of photosynthesis, also known as the Calvin cycle. It describes how Melvin Calvin used radioactive carbon dating in the 1940s-1950s to trace the pathways of photosynthesis. His experiments involved growing algae in a device called a "lollipop apparatus" with carbon-14 labelled CO2 to analyze the compounds the radioactive carbon entered. The document also provides an overview of the key molecules and ratios involved in the Calvin cycle, which occurs in the stroma of the chloroplast and can continue in the dark.