Youth in Dresden; emigration to New York; study at Columbia University. Travel to Europe, 1925; contacts with Wolfgang Pauli, Alfred Land.̌ Work on dispersion theory, 1926-1927; Copenhagen, 1927; Hendrik Anthony Kramers. Interest in molecular physics. Assistant to Pauli; Pauli and solid state physics; contacts with Paul Scherrer and Gregor Wentzel. Work on "predissociation" (Victor Henri). Handuch article; the Kronig-Penney model; Grn̲ingen, Leiden, Delft; Gorter; physics in Holland in the 1930s. This interview was conducted by Michael Ekert in 1991.