Focus of J. Robert Oppenheimer

ATOM

The tiny building block he split to change history forever.

J. Robert Oppenheimer was the physicist who led the Manhattan Project, the World War II effort to develop the first atomic bomb. The clue points to his primary scientific focus—the structure and energy of the atom—which became the foundation of nuclear physics. "Atom" is the straightforward answer, referencing both his research and the weapon he helped create. No wordplay here, just a direct historical connection.