I.E. Tamm is one of the great figures of 20th century physics and the mentor of the late A.D. Sakharov. Together with I.M. Frank, he received the Nobel Prize in 1958 for the explanation of the Cherenkov effect. This book contains a commented selection of his most important contributions to the physical literature and essays on his contemporaries - Mandelstam, Einstein, Landau, and Bohr - as well as his contributions to Pugwash conferences. About a third of the selections originally appeared in Russian and are, to our knowledge, for the first time now available to Western readers. This volume includes a preface by Sir Rudolf Peierls, a biography compiled by Tamm's former students, V.Ya. Frenkel and B.M. Bolotovskii, and a complete bibliography.