Scientists holding the container with the plutonium core that was to be the heart of the Fat Man atomic bomb. Image taken on the island of Tinian, August 1945. At right is physicist Harold M. Agnew, later to become the director of Los Alamos National Laboratory. The portion of the image showing the container itself had been scratched out by the FBI in 1946, in an effort at secrecy. Now, of course, this photo is declassified, as are all the materials published here.
(Agnew also managed to sneak a camera onto Bockscar, which was used by one of the crew to take the photos of bomb damage. No one on the plane knew how to operate the official camera because the official cameraman was not on the plane.)
Photo from Harold Agnew. All images courtesy of the Los Alamos National Laboratory