In 1926, Fermi discovered the statistical laws, now called Fermi statistics. These laws explain the actions of the particles which are subject to the Pauli exclusion principle, which are now called fermions. These are different to the particles called bosons which are explained by Bose-Einstein statistics. In 1927 he became Professor of Theoretical Physics at the University of Rome. He spent time studying electrodynamics, and began to closely look at the atomic nucleus. In 1934, using discoveries made by Wolfgang Pauli, Frédéric Joliot, Irène Joliot-Curie, he was able to show changes in almost every element bombarded with neutrons. This led to the discovery of slow neutrons, nuclear fission and making elements that were not in the Periodic Table.