Not too long ago, Saoirse Ronan found herself face-to-face on a red carpet with mega star Jennifer Lopez.

"She didn't have a clue who I was," said the young Irish actress, who has earned her second Oscar nomination in the haunting and sweet immigrant film "Brooklyn."

"I was like, 'J-Lo!' She was like, 'Yes?'" recounted Ronan.

And then, in her gorgeous, lilting accent, the young actress dropped a mini-bombshell on Jenny From the Block: "I'm from the Bronx, too."

"She's like, 'Oh, OK,'" said Ronan. "I said, 'Yeah. We're from the same block.' She didn't have a clue what I was talking about but I was delighted that we shared in that for a second — or at least I did."

J-Lo — like many of us — are definitely starting to get a clue about this New York-born, thoroughly refreshing 21-year-old. This month, she's started work on her first stage role.

Something easy to start with, perhaps? "No. I can never do that, can I?" she said, laughing.

No, Ronan has decided to star on Broadway in a revival of Arthur Miller's "The Crucible," considered among America's best plays. And she'll be playing Abigail Williams, the vengeful fulcrum of the play. Previews begin Feb. 29.

"What I wanted to do was go to a small, little theater and do a new play and have it be something that nobody paid attention to, just to get me into it," said the actress with striking blue eyes.

"Then this came along and you kind of can't say no. I don't know. Maybe it's a good thing to be thrown in the deep end because then you're just exposed to everything."

Directed by Dutch visionary Ivo van Hove, the revival will also star Ben Whishaw, Sophie Okonedo, Ciarán Hinds, Tavi Gevinson and Jim Norton. It will have an original score by Philip Glass.

The multi-talented Gevinson, who plays Mary Warren, is making her second Broadway appearance and said that if Ronan is fighting any nerves, it's not apparent. "When Saoirse is on that stage, I'm genuinely scared of her. She's got nothing to worry about."

Born to Irish parents in the Bronx, Ronan's family moved back to Ireland when she was 3. Her career breakthrough came in the 2007 film "Atonement," playing a tween who coolly tears apart lovers. She earned an Oscar nomination.

Ronan, whose first name is pronounced SUR'-shuh, was also in "The Lovely Bones," ''Hanna" and "The Grand Budapest Hotel." Awaiting release is a film adaptation of "The Seagull." She is clearly an actress drawn to subtle shadings.

"I knew from an early age what I didn't want to do," she said. "Unless the right one came along, the idea of doing a franchise or anything like that for me wasn't something that appealed to me."

When she was 12, before she got "Atonement," Ronan was offered a part in an action film. "It was all fire and guns and I was the kid that was rescued. I knew then that I didn't want to do that. I wanted to play the strange child that ruins everyone's life."

The glitz and glamor part of acting doesn't interest her. "The Hollywood side of it is weird," she said and has moved to New York. "I don't feel like I'm part of that world."

Her leap into theater is partly due to her father's influence. Paul Ronan was a one-time bartender who so impressed actors who came in for a pint than they convinced him to start acting. His first gigs were in the theater before he branched out to such films as "The Devil's Own" and "Veronica Guerin."

"He would tell me stories about his experiences in the theater — how draining it can be and how exhilarating it can be at the same time," she said. "When he talks about that, his whole face lights up."

Ronan had been offered stage scripts before but decided she wasn't ready until now. "I needed to at least be an adult to take it on and be experienced enough at just acting. I always had it in my head, 'I'll do a play when I'm about 21 or 22.' And it's perfect."

It happened this way: While doing press for "The Grand Budapest Hotel," she met movie and theatrical producer Scott Rudin, a big admirer. The next day, he sent an email asking if she'd do a play, but never said what he had in mind. A few days later he revealed "The Crucible," a searing portrait of a community engulfed by hysteria.

"It's very different to film in the sense that it's ongoing and it's ever-changing and it's ever-growing, whereas with film acting, you build up and you build up and you work on it and then you do your few takes and then it's done," she said. "So I think it took me a second to wrap my head around the fact that this feels like a living, breathing thing."