Kelly Clarkson got her start as the winner of the very first season of American Idol, so it totally makes sense that she would make an appearance at the very last season. She swung by the set last night for an emotive performance of "Piece by Piece," the most heartbreaking song and title track on her last album.

In it, Clarkson details how she felt as a kid when her dad left. She was six at the time, and begins with a deeply saddening, "And all I remember is your back / Walking towards the airport leaving us all in your past." 

The song goes on to detail Kelly's first pregnancy and her daughter, promising never to abandon her. It's heavy stuff, and it made her cry while singing it. She's not the only one: judge Keith Urban teared up, too.

Watch the performance above, then click through our American Idol Season 1 retrospective: Where Are They Now?