On December 4, 1930 Pauli wrote the famous letter "Dear Radioactive Ladies and Gentlemen" to physicists who met in Tübingen. He speculated the hypothesis of the existence of a new particle, currently known as the neutrino. At the time, Pauli considered his idea too immature to be published. Pauli proposed a new particle to explain the non-conservation of energy during beta decay. Even without being detected, it does not have electric charge and very little mass, neutrinos carrying part of the energy. This actually happened 26 years before Fred Reines and Clyde Cowan claim the first detection of neutrino in 1956. The Japanese Takaaki Kajita and the Canadian Arthur McDonald received in 2015 the Nobel Prize in Physics for the discovery of neutrino oscillation, which shows that these particles have mass. The discovery of both physicists changed our understanding of the deepest operation of matter, since neutrinos have mass, contrary to what was thought for decades. McDonald and Kajuta managed to refute the established theory that neutrinos lacked mass to the point of discovering that different neutrinos have different characteristics, through direct observation of solar particles.