Shortly after the first nuclear test was conducted in the small town of Los Alamos in New Mexico, USA, atomic bombs were used for the first time over the Japanese cities of Hiroshima and Nagasaki.
Up to 215,000 people die and the consequences for the survivors will be devastating for decades to come.
Since then, nuclear weapons have not been used in war, but more and more countries have become nuclear-weapon states since the end of World War II.
Click on the clip to see how the atomic bomb spread around the world and see more about the nuclear weapons in the Foreign Office: The peace bomb on SVT Play from 7.30 pm or 10 pm on SVT2.