The principle of the nuclear energy was invented by famous german scientist Albert Einstein in 1905. In his Special theory of relativity explained, that little amount of the substance can be theoretically transformed to a big amount of the energy. Nuclear disintegration (rozpad) is practical application of the Einstein’s theory and that was Enrico Fermi, who managed, for the first time, to realize it in 1934. But in a fact Fermi didn’t realize (uvedomiť) it. In the year 1939 the scientists confirmed (potvrdili) that it’s possible. This information was top secret because of coming of the W.W.II. Fermi and other scientists went to the U.S.A. On the Einstein’s urging began intensive research there, in hope that Germany don’t construct the nuclear bomb as first. First nuclear bomb was tested in the U.S. in July 1945, soon after the defeat of the Third Empire. But it was Japan, who as first and until these days the only tasted the horror of the nuclear weapons. H-Bomb was for the first time tested in 1952. First nuclear reactor, which was producing the electricity, was built in the U.S.S.R.