Kelly Clarkson brought everyone to tears as she sang 'Piece by Piece' on 'American Idol'.

Kelly Clarkson

Kelly Clarkson

The 33-year-old star - who shot to fame when she won the first series of the programme in 2002 - sobbed during the performance and made judges Jennifer Lopez and Keith Urban cry too, during a special appearance on the 15th and final season of the talent show last night (25.02.16).

And afterward, show host Ryan Seacrest praised Kelly - who is pregnant with her second child - for the "incredible" and emotionally charged performance.

Kelly replied: "I'm pregnant and it's nostalgic and I can't believe it's the last season. Yeah, really sorry I just bawled."

The song has a strong meaning to the star - who already has 19-month-old daughter River Rose with husband Brandon Blackstock - and she previously revealed she wrote it as a homage to Brandon's great parenting.

Kelly even missed the Grammy Awards - for which she was up for Best Solo Performance for 'Heartbeat Song' and Best Pop Vocal Album for 'Piece by Piece' - to sing 'Piece By Piece' on the talent show and be a guest judge for the episode, because doctors said she had to take rest and cut down on work.

Speaking recently, the 'Breakaway' singer said: "I was going to do the Grammys and 'Idol', and then my doctor was kind of like, I just have such hard pregnancies, flying back and forth to LA, like if they were closer together, I would've done both, but I had to kind of choose one.

"I obviously chose 'Idol' because it's ending and I was the original winner, so it'd kinda be weird if I wasn't there."