Later This site tells the story of the history of the universe. Click Earlier and Later to follow the story. Nuclear fusion first occurred during the Big Bang about three minutes after the macrocosmos began. It also occurs inside stars , and is the main way in which stars convert matter energy into light.
Nuclear fusion occurs in hydrogen bombs.
Much work is currently going on to try to make nuclear fusion happen on Earth in a controlled way. Scientists believe that a great deal of energy will be released in this way with very little pollution. The main fusions within a star are described here. The positron would fly away until it met an electron, when the two of them would annihilate each other and their energy would be converted into radiation. There are many different ways in which fusion can occur.