In autumn of 1949, Enrico Fermi returned to Italy after an eleven-year absence to deliver nine lectures, six in Rome and three in Milan. Apart from subsequent limited publication, this material has been little seen by the larger scientific community. This volume represents the first time that these nine lectures have been published in English. The nine lectures collected in this book represent a precious document of Fermi’s view on topics with which he had engaged in the previous decades. They were addressed to the young Italian physicists and to a more general audience only then beginning to recover from the physical and moral disruption of the war. Published in collaboration with the Italian Physical Society (SIF), the book includes a presentation of the president of SIF, an introduction written by the editors, and two substantial essays: one on Fermi’s life, and a second on Fermi’s skill in talking about Physics in a clear and sparkling manner. The volume appears as a contribution to the 70th anniversary of Fermi's death, and should appeal not only to students of physics, but to both those with an interest in the history of science in general and those who wish for a clearer picture of the life and mind of this pioneering physicist.