This edition of the private and scientific correspondence of Sir Rudolf Peierls gives a unique insight into the life and work of one of the greatest theoretical physicists of the 20th century. Rudolf Peierls' scientific work contributed to the early developments in quantum mechanics, and he is well known and much appreciated for his contributions to various disciplines, including solid state physics, nuclear physics, and particle physics. As an enthusiastic and devoted teacher, he passed on his knowledge and understanding and inspired the work of collaborators and students alike. As an effective administrator he was responsible, almost single-handedly, for the establishment of an outstanding successful centre of theoretical physics in Birmingham, and later contributed much to theoretical physics in Oxford.A meticulous collector of correspondence, Sir Rudolf left a fascinating collection of letters, in some cases spanning more than seven decades. This collection includes correspondence with his parents, his wife, the Russian-born physicist Genia Kannegieser, life-long friends such as Hans Bethe, and many great physicists, including Wolfgang Pauli, Niels Bohr, Werner Heisenberg, Lev Landau, and George Placzek, to name but a few.This first volume, which covers the years 1922 to 1945, contains much of the early family correspondence, letters exchanged between Rudolf and Genia Peierls before and after their marriage in 1931, correspondence relating to early developments in quantum physics, and interesting material relating to the development of nuclear weapons. The extensive apparatus provides an invaluable background which allows the reader to put the presented documents into their multi-faceted social, political and scientific context.