The Irish actor plays Robert J. Oppenheimer, the titular physicist whose secret laboratory invented the atomic bomb during WW2.
Little Women and Midsommar star Florence plays Jean Tatlock, a psychiatrist and member of the communist party who Oppenheimer had a love affair with, both before and during his marriage.
Speaking to the Sydney Morning Herald ahead of the film’s release on Friday, Cillian addressed the much-talked about sex scenes – which it was previously reported will feature “prolonged, full nudity” from Cillian and Florence and have earned the film an ‘R’ rating, the US equivalent of a 15+.
“Those scenes were written deliberately,” he said. “[Nolan] knew that those scenes would get the movie the rating that it got. And I think when you see it, it’s so fucking powerful. And they’re not gratuitous. They’re perfect.”
Cillian also praised his co-star Florence as “just amazing” and “fucking phenomenal,” adding that he’s enjoyed her work since the 2016 drama Lady Macbeth.
He said: “She has this presence as a person and on screen that is staggering. The impact she has [in Oppenheimer] for the size of the role, it’s quite devastating.”
Oppenheimer is Nolan’s 12th feature-length film – and his longest – but his first to include sex scenes.
The director previously explained his decision to feature the intimate moments in the biopic as he told Insider they are “essential” to understanding Oppenheimer’s life as a whole.
“His very intense relationship with Jean Tatlock [...] is one of the most important things in his life,” he said. “But not least for the fact that Jean Tatlock was very explicitly a Communist and his obsession with her therefore had enormous ramifications for his later life and his ultimate fate.
“It felt very important to understand their relationship and to really see inside it and understand what made it tick without being coy or allusive about it, but to try to be intimate, to try and be in there with him and fully understand the relationship that was so important to him.”
Nolan was also full of praise for Florence, as he added: “I met with her and immediately felt a creative connection. [...] And she was just fantastic to work with.”
Oppenheimer is released in UK cinemas on Friday 21 July.