See Cillian Murphy as J. Robert Oppenheimer in First Trailer for Christopher Nolan's New Thriller

The trailer for Christopher Nolan's atomic-bomb thriller Oppenheimer has just dropped.

In a preview of Universal's epic story of J. Robert Oppenheimer, the Manhattan Project mastermind who helped develop the A-bomb, moviegoers are getting a first-look at Cillian Murphy as the titular scientist.

As images from the movie flash alongside a countdown clock, a voiceover ominously describes the character as "the most important man who ever lived," while a tagline reads, "The world forever changes."

Murphy, 46, reunites with Nolan after starring in three films for the director: 2005's Batman Begins, 2010's Inception and 2017's Dunkirk.

"I'll always turn up for Chris, whatever the size of the part," Murphy told Variety in February. "Chris will call me up and I'm there. Isn't it wonderful that filmmakers are still making challenging, demanding films within the studio system, shot on film?"

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"I think he's flying the flag," added the Irish actor of Nolan, 51. "Him, Paul Thomas Anderson and Quentin Tarantino are fantastic filmmakers making interesting work on a massive scale."

Based on the Pulitzer Prize–winning book American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer by Kai Bird and Martin J. Sherwin, the film features a large cast including Emily Blunt as Oppenheimer's wife, Katherine; Robert Downey Jr. as Lewis Strauss, a major figure in the development of nuclear weapons, according to IMDb; and Matt Damon as Lt. Gen. Leslie Groves, who oversaw the construction of the Pentagon and directed the Manhattan Project.

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Florence Pugh, Josh Hartnett and Rami Malek also star in the film.

Oppenheimer opens in theaters July 21, 2023.