1930-1937: the first $\beta$-rays and neutrino theories

The conceptual bases of Fermi’s $\beta$-ray theory (at its 90th anniversary) are examined, highlighting the innovative drive and inspirational role for the progress that followed just afterwards. Moreover, the three different ideas of the neutrino born from the proposals of Pauli 1930, again Fermi 1933 and Majorana 1937 papers are discussed, emphasising the interest of the latter for current expectations.