In the 1920s, a Russian biologist studying onion roots made a surprising discovery: underground, down in the darkness, it seemed like the cells inside the onion roots were making their own … light. The “onion root experiment” went on to become something of a cult classic in science, and eventually the biologically-made light was dubbed “biophotons.” In the ensuing century, biophoton discoveries moved from onion roots to bacteria, frog embryos, and humans. Today, scientist Nirosha Murugan is on a career-defining journey to learn more about the light. As she and her colleagues study this mysterious phenomenon, they find themselves...