Matt Damon credits Cillian Murphy for keeping his sanity during the filming of "Oppenheimer."

Cillian Murphy plays scientist J. Robert Oppenheimer in the Christopher Nolan period piece epic.

Murphy's dedication to the role was intense, leaving his brain "too full" to join the cast for dinners.

Damon describes Murphy's performance as a "marathon" masterclass in acting.

Emily Blunt, another co-star, acknowledges the monumental weight Murphy had to shoulder.

Murphy felt overwhelmed by the responsibility of such a significant role.

Murphy had a long-standing collaboration with Christopher Nolan, spanning 20 years and various films.

The actor was eager to lead a Nolan film and considered it the right time to take on a bigger responsibility.

Murphy's commitment to working with Nolan was unwavering, regardless of the size of his role.

Murphy's desire to play a lead role for Nolan was a secret ambition.

Murphy's portrayal of Oppenheimer in "Oppenheimer" fulfilled his deep-seated wish.