The casting process for “Twilight” was all about chemistry.

In a new profile on Kristen Stewart in The New Yorker, the “Spencer” star looks back on her role as Bella Swan in the blockbuster franchise, and how Robert Pattinson ended up as Edward.

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“To cast Edward, [director Catherine] Hardwicke had actors come to her house in Los Angeles to read with Stewart and make out,” the article explains.

“It was so clear who worked. I was literally just, like…” Stewart says, imitating swooning for the journalist.

She adds that Pattinson had an “intellectual approach that was combined with ‘I don’t give a f**k about this, but I’m going to make this sing.’ And I was, like, ‘Ugh, same.’”

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That quality in their audition evidently made the actors perfect for the film, Stewart explains.

“And, whatever, we were young and stupid and, not to say that we made it so much better, but that’s what it needed, and that’s what anybody playing those parts needed to feel,” she says.

Stewart and Pattinson, who are also exes, starred in the franchise’s five films.