'Oppenheimer' cast on Christopher Nolan’s epic, unconventional atomic bomb biopic

The countdown for Christopher Nolan’s atomic bomb biopic, "Oppenheimer," is quickly winding down, as the film releases in theaters and IMAX screens everywhere Friday.

In anticipation of its release, the main cast spoke to ABC Audio ahead of the SAG-AFTRA strike about the three-hour epic.

Cillian Murphy is no stranger to working with Nolan -- though this was his first time taking on a leading role in one of his films.

That role is J. Robert Oppenheimer, the father of the atomic bomb.

"Chris calls me up, and whatever he asks me to do, I’m there for him. That’s how much I love his work and that’s how much respect I have for him," Murphy said.

"We’ve done six movies now, but I did not expect this one to be the lead. So, it was a great — a very pleasant shock," he continued.

And while the film follows true events, Murphy says Oppenheimer is "not your conventional biopic."

"It does make you think," he said. "And people can choose to think about the nuclear age that we live in, or they could choose not to. And I think this film might affect that choice."

His co-stars Matt Damon and Emily Blunt wholeheartedly agree on the film’s importance.

"It is the biggest story, I think, of the last hundred years, if not in the history of humanity, right?" said Damon, who plays Leslie Groves, a lieutenant general who served as director of the Manhattan Project, in the film.

"It’s knowing you’re going to be a part of something so important. It is so exciting," Blunt, who plays Kitty, Oppenheimer's wife, added.

Of the film's director, Damon noted, "A story of that scale deserves a director of that ability."

"Oppenheimer" arrives in U.S. theaters on July 21.