In the 1920s, you could buy radioactive toothpaste, radium-laced water, and uranium-glazed dinnerware. Radiation was a health fad, a miracle ingredient, and a marketing gimmick. Two decades later, it destroyed Hiroshima. The journey from consumer novelty to civilization-threatening weapon is one of the fastest and most terrifying transformations in the history of science.

This episode traces the arc of radiation from its discovery through the consumer craze, the Manhattan Project, and the bomb that made the world realize what it had been brushing its teeth with.

• The early radiation fad — radium water, radioactive cosmetics, and the Radium Girls who paid the price
• The scientific breakthroughs that revealed radiation's true power
• The Manhattan Project and the weaponization of atomic energy
• Hiroshima, Nagasak ...