Dieter Gruen joined the Manhattan Project at Oak Ridge in September of 1944, shortly after his graduation from Northwestern University. His work primarily focused on the chemical problems related to the separation of uranium isotopes. In response to difficulties determining the difference between uranium nitrate and uranium peroxide in the final stages of separation, Gruen created an entirely new material: sulfonated copper phthalocyanine. This indicator maintained stability in nitric acid, allowing for the easy identification and eventual extraction of uranium nitrate. Immediately after the war, he helped form Oak Ridge Scientists and Engineers, a group dedicated to ensuring the future prevention of the use of nuclear weapons in war. In this interview, Gruen discusses the secrecy related to the project, the relatively lax safety standards of the period, and the differences between government support for science in the 1950s and government support today.