"Little Boy", the atomic bomb dropped on Hiroshima
1. A detonator was used to trigger the explosion.
2. One mass of uranium was fired into the other.
3. The neutrons created by that firing started a fission chain reaction, generating a tremendous amount of energy instantaneously.
http://www.pcf.city.hiroshima.jp/kids/KPSH_E/hiroshima_e/sadako_e/subcontents_e/images_e/genbaku_e.swf
URL: http://www.pcf.city.hiroshima.jp/kids/KPSH_E/hiroshima_e/sadako_e/subcontents_e/06hiroshimagen_1_e.html
