<AREA SHAPE=RECT COORDS="3,225,18,239" HREF="!Hiroshima, Japan, was largely destroyed by a gun-type fission bomb called the Little Boy bomb on Aug. 6, 1945. The bomb was dropped from a B-29 bomber. When the bomb reached 1,850 feet (564 meters), a radar echo set off an explosive inside. This explosive drove a wedge of U-235 into a larger piece of U-235, setting off the nuclear blast.">
<AREA SHAPE=RECT COORDS="320,223,335,240" HREF="!Nagasaki, Japan, was struck by an implosion-type fission bomb called the Fat Man bomb on Aug. 9, 1945. In this bomb, an explosive crushed a hollow sphere of plutonium into a core made up of the chemical elements beryllium and polonium. This core then released neutrons, which triggered a fission chain reaction in the plutonium.">