Derek Muller introduces uranium and its use throughout history. Uranium, originally sourced from pitchblende, became the subject of intense scientific study. Using computer-generated dragons as a metaphor for daughter isotopes, the episode shows how uranium turns into lead in the process of radioactive decay. The harmful effects of radiation from radium, which is produced during the decay of uranium, are discussed. Derek shows what the first atom bomb looked like. The episode concludes with the use of uranium as a nuclear weapon and the bombing of Hiroshima at the end of World War II.