Exclusive footage: Why Christopher Nolan's 'Oppenheimer' is 'the most important story of our time'

In case you were on the fence about Christopher Nolan's historical thriller "Oppenheimer," Matt Damon calls it "arguably the most important story of our time." So buckle up for a brainy, important ride.

Written and directed by Nolan, "Oppenheimer" (in theaters July 21) chronicles the 1940s origins of the atomic bomb and physicist J. Robert Oppenheimer's work with fellow scientists as part of the Manhattan Project. A new video featurette (debuting exclusively at usatoday.com) reveals fresh footage plus digs into the film's plot, use of practical effects and real locations (such as the campus of Princeton University and Oppenheimer's house in New Mexico), and the A-list cast Nolan has assembled to tell his story.

"It’s profound but it’s told in a very human way," says Cillian Murphy, who stars as Oppenheimer, while Robert Downey Jr., cast as Lewis Strauss, a founding commissioner of the U.S. Atomic Energy Commission, reports that "everything Christopher Nolan has done has been a prelude to this."

"This is I think a definitive moment in the history of modern filmmaking."

The cast also includes Damon as Manhattan Project director Lt. Gen. Leslie Groves Jr., Emily Blunt as Oppenheimer's biologist wife Kitty, Florence Pugh as psychiatrist Jean Tatlock, Benny Safdie as theoretical physicist Edward Teller and Josh Hartnett as nuclear scientist Ernest Lawrence.

Nolan revealed at CinemaCon that he became interested in making "Oppenheimer" when he learned that, in the leadup to the 1945 Trinity Test (the first detonation of a nuclear weapon), there was a slight possibility that by pushing the button they'd set fire to the Earth's atmosphere and blow up the planet – and pushed it anyway.

“I know of no more dramatic tale,” Nolan said at the Las Vegas convention for theater owners. "I wanted to be there with them in that room and see what that would have been like.”

'Oppenheimer': Christopher Nolan previews his film about 'the most important person who’s ever lived'

This article originally appeared on USA TODAY: 'Oppenheimer' exclusive video: Christopher Nolan tackles atomic bomb