Billie Eilish tells Jimmy Fallon how her 'Barbie' soundtrack song inspired the film's memorable montage

Billie Eilish was on The Tonight Show Starring Jimmy Fallon Thursday, where she broke down the process of writing her song for the hit film Barbie and how her track helped create one of its most memorable scenes.

Eilish, who's in town to be the musical guest for this week’s episode of Saturday Night Live, sat with Fallon to talk about what went into making her song, “What Was I Made For?” from the Barbie soundtrack, and also hinted at a new album being in the works as well.

The song that changed Barbie

After rattling off stats like it being number one for 14 weeks on the Billboard charts, getting nominated for five Grammy awards and being streamed over two billion times, Fallon declared “What Was I Made For?” the “song of the year.”

And while Fallon’s dream scenario of Eilish singing the opening line to herself and immediately knowing that she had a hit on her hands wasn't quite accurate, the singer said it “felt good” but that it was a much more chill process.

Eilish said that one day last January she and her brother and writing partner, Finneas, met Barbie director Greta Gerwig at the movie studio where they watched roughly the first 30 minutes of the film along with some other key scenes.

Gerwig told them, “I really want Barbie’s heart song,” and Eilish said that description really stuck with them over the next 24 hours, despite the fact that much of that time was filled with writer’s block. Eventually, Eilish said, they decided to take another stab at the song and that’s when Finneas sat down at the piano and played the opening chord. From there she started figuring out the melody and the rest was history.

Eilish said that one of the scenes they watched before writing the song was one toward the end with Margot Robbie’s Barbie and Rhea Perlman’s Ruth Handler (Barbie’s original creator), which sets up the memorable montage that’s been dubbed the Real Women Montage by many, and has Eilish’s song playing over it.

But Eilish revealed that before they turned in their song, that scene ended with just a shot of Robbie and there was no montage to speak of.

“They added a scene, that montage, from your song?” Fallon asked.

“Yeah, like all the footage of people living during the song, that was all added after the song,” Eilish confirmed.

Making the montage

In Barbie, after Pearlman’s character delivers iconic lines like, “We mothers stand still, so our daughters can look back to see how far they’ve come” and, “Take my hand, close your eyes, and now, feel,” Eilish’s “What Was I Made For?” begins playing over a memorable montage.

Gerwig told Entertainment Weekly that the montage features real home videos submitted by the film’s cast and crew and shows them surrounded by their family and friends. Which is why critics and most other media have named it the Real Women Montage.

While the footage is powerful, the song is seemingly what makes it so great — Fallon admitted to shedding a tear when he experienced the moment — and Eilish said that the song has connected with fans like no other one she’s ever recorded.

“I feel like it brought women together in this way that I feel like I haven’t felt part of like that, and it made me feel really good,” Eilish said. “And I also felt like it was bringing, like, people together. It felt like we were all experiencing the life experience.”

Billie’s future plans

Most of the conversation was about the Barbie song, but Fallon did manage to get an update on Eilish’s next studio album, which would be her third.

“We are almost done with this new album we’re making,” Eilish said about herself and Finneas, much to the delight of audience members and Fallon.

And for her immediate future, Eilish is slated to perform as the musical guest for the final SNL episode of the year, with former cast member Kate McKinnon hosting for what will be her first time.

And just in case you were wondering — because you know Fallon was — Eilish confirmed that she will be performing “What Was I Made For?” on SNL.

The Tonight Show Starring Jimmy Fallon airs weeknights on NBC.