Early interest in science; training in physics and graduate work at Johns Hopkins, courses, books ,seminars,informal atmosphere,1927-33; summer work in spectroscopy labortory at National Bureau of Standards,1929; interest in elementary particles, attraction of nuclear physics,1933;post-doctoral work with G.Breit on pair theory; New York University 1933-34; potential well model and its application to experimental results,1933-35; studies at Bohr Institute,Copenhagen 1934-35; discussions in Copenhagen on electrodynamics; role of experimental results in formulation of Bohr’s concept of compound nucleus, 1935; reasons for initial sceptical reaction to compound nucleus model; significance of Bethe-Bacher-Livingston review articles in REV. MOD. PHYS. 1936-37; development of compound nucleus idea after 1935; use-of compound nucleus and Breit-Wigner formula as guide for experiment; development of collective model; reaction to Yukawa’s 1935 meson theory and subsequrnt new cosmic ray particles; establishment of cosmic ray laboratory at Princeton, 1945; work considered personally satisfying; scattering matrix and other work at Univ. of North Carolina, 1935-38; close relationship of physics and mathematics departments at Princeton, 1938- ; collaboration with Bohr on theory of fission,1939; relation of fission physics to other aspects of nuclear physics; plans of physicists for postwar work.