New Zealand physicist Ernest Rutherford was among the first to realise that the atom was not solid, but consisted of a single, central nucleus surrounded by orbiting electrons. In 1919 he became the first person to split the atom artificially, thus proving that the atomic nucleus itself was made up of a number of smaller particles. Scientists began to work on harnessing the energy produced by splitting the atom. Nuclear fission - splitting the nucleus of an atom - was discovered by Otto Hahn and Fritz Strassmann in 1938. Their discovery opened the way for atomic energy and atomic bombs.