The recorded death tolls are estimates, but it is thought that about 140,000 of Hiroshima's 350,000 population were killed in the blast, and that at least 74,000 people died in Nagasaki.
The bombings brought about an abrupt end to the war in Asia, with Japan surrendering to the Allies on 14 August 1945.
But critics have said that Japan had already been on the brink of surrender.
Those who survived the bombings are known as hibakusha. Survivors faced a horrifying aftermath in the cities, including radiation poisoning and psychological trauma.
British photo-journalist Lee Karen Stow specialises in telling the stories of women who have witnessed remarkable events in history.
Stow photographed and interviewed three women who have vivid memories of the bombings 75 years ago.