60 years ago today, the Soviet Union tested the most powerful nuclear weapon in history: the Tsar Bomba. Here's how it happened. | Radio Free Europe/Radio Liberty

On July 25, 1946, the first underwater nuclear explosion was conducted at a depth of 27 meters in the Bikini Atoll lagoon, shortly after the end of World War II. The over 100 indigenous residents of Bikini Atoll were relocated to other islands to facilitate the nuclear testing. | History In Pictures