Quantum physics divides the microscopic world into bosons and fermions. The elementary constituents of matter are fermions: the structure and impenetrability of bodies is due to the electrons of the atoms that refuse to give space to their neighbours. The mediating particles of the fundamental forces are bosons.
Between 1923 and 1925 Fermi published important contributions to quantum theory which, at the beginning of 1926, led to the formulation of the statistics that bears his name. In this fundamental work, starting from ideas on the statistical mechanics of a system of identical particles – ideas that Fermi had already begun to develop at the institute directed by Paul Ehrenfest in Leiden – Fermi introduced into the description Pauli’s ‘exclusion principle’ , namely the selection rule hypothesized at the beginning of 1925, which allowed him to found an exhaustive theory of the behavior of those particles which, from that moment on, will take the name of “fermions”.
A few months later, in a completely autonomous way, the English physicist Paul Adrien Maurice Dirac will come to the same conclusions. Today the theory bears the name of ‘Fermi-Dirac statistics’.