An atomic bomb is a powerful weapon that releases energy through nuclear reactions, specifically fission, where the nucleus of an atom splits into smaller parts. This process releases a massive amount of energy, resulting in a devastating explosion. The first atomic bombs were developed during World War II as part of the Manhattan Project. The use of atomic bombs in warfare occurred in 1945 when the United States dropped bombs on the Japanese cities of Hiroshima and Nagasaki. These bombings led to significant loss of life and destruction, ultimately contributing to the end of World War II. The aftermath raised ethical questions about nuclear weapons and their impact on humanity.