The Deepwater Horizon oil rig explodes. The explosion of the British Petroleum (BP) platform operated by Transocean killed 11 workers and led to the largest accidental marine oil spill in history.

15 die in the Columbine High School massacre. A further 24 victims were injured when two teenagers opened fire on students and teachers in the high school south of Denver.

Soviet air defense shoots down Korean Air Lines Flight 902. The Boeing 707's crew had miscalculated their route, taking them into Soviet airspace at the height of the Cold War. The jet made an emergency landing on a frozen lake. Two passengers were killed in the incident.

A human organ is surgically reconstructed for the first time. Romanian surgeon Dan Gavriliu used a section of the stomach to bypass the esophagus.

Pierre and Marie Curie discover the radioactive element radium. In 1903, the French couple received the Nobel Prize in Physics for their pioneering research.