Taylor Swift performed 'As Tears Go By' with the Rolling Stones at Chicago's United Center on Monday night (June 3), engaging in a sweet and ethereal little dance with frontman Mick Jagger. In the space of one song, genres and generations collided on a stage in the Midwest.

Jagger prefaced the song by saying that they were going to slow things down and do "a bit of a ballad" that they have not performed in quite some time. He then said they would do so with an assist from a young lady, setting the table for Swift.

Dressed in a cute, short and tight black number, Swift engaged in a harmlessly suggestive dance with the rock star, who is known as quite a ladies man. It was a quieter song than you might expect from those rockin' Stones, but it was definitely more Swift's speed. Her dance -- namely the partial bow at about 2:20 in -- was especially sweet.

Swift floated on stage, waving and extending her arms in a flowy fashion as she and Jagger waltzed from one side to the next.

The over-the-moon singer tweeted a black and white photo of herself and Jagger, captioning it: "Filing this under 'friends forever.'" What a pair!

She added: "Filing this under 'never in my wildest dreams'.Thank you @RollingStones for inviting me to Chicago to sing with you." From the looks of it, they were glad to have her, too. Even for a girl like Taylor Swift, who seems to have it all, performing with the Rolling Stones is a dream come true.

Just a few weeks ago, the Stones invited country's Carrie Underwood to sing ‘It’s Only Rock ‘n’ Roll (But I Like It)' with them in Toronto. Watch here.