Christopher Nolan's 'Oppenheimer' promises to be his most important film yet.

Christopher Nolan revealed at CinemaCon that his upcoming film, Oppenheimer, is about J. Robert Oppenheimer, the theoretical physicist known as “father of the atomic bomb” who led America’s efforts in the nuclear arms race during World War II. The film stars Cillian Murphy in the title role along with a star-studded supporting cast and will debut its first full trailer in theaters ahead of Guardians of the Galaxy Vol. 3 on May 5. Nolan called Oppenheimer “the most important person who ever lived” and said his story has to be seen to be believed.