ABC News' Anna Wild reports:
What stole the show at the 55th Annual Grammy Awards in Los Angeles was the huge silver gown the 29-year-old singer wore while performing her hit "Blown Away."
As Underwood segued into her single "Two Black Cadillacs," the audience at the Staples Center and the millions watching on TV realized why her gown was so big: It became a "screen" onto which various images were projected, ranging from roses to butterflies to fireworks.
The man behind the high-tech, one-of-a-kind gown had days to make it.
"We got the call on a Friday two weeks ago that we need the dress in a week," designer Don O'Neill told ABC News' Amy Robach.
O'Neill, a New York-based designer originally from Ireland, was told that Underwood wanted "something unique" and something that could have a movie projected on it.
He got to work creating a silver-gray Duchess satin gown inspired by the Freedom Tower in New York City, the 1,776-foot-tall tower on the site of the former World Trade Center.
"I love that sort of triangular shape that gets narrower in the Freedom Tower," O'Neill said. "And I wanted something that's to me the ultimate modern piece of Manhattan."
In the end, Underwood's dress had more than 100 yards of tulle and crinoline inside of it to support the 4-and-a-half-foot-wide skirt needed to be large enough to project the images. The dress' corset featured thousands of crystals, each hand-sewn.
Underwood's look that Grammy watchers saw on Sunday night took a team of four 80 hours to complete.
"Tears," O'Neill said of his reaction when he saw Underwood, in his dress, on stage.
The man behind the dress' technical magic was Underwood's creative director, Raj Kampoor.
"I thought, 'Oh, wouldn't it be cool if Carrie wasn't stuck in the same dress for the whole performance,'" Kampoor told Robach.
Two projectors hung from the ceiling of the Staples Center, 70 feet from the main stage, and projected the images onto Underwood's dress, each image timed perfectly with Underwood's music.
Another secret to the musically and technologically masterful performance?
Underwood, usually not one to stand still while performing, had to stand in one place, atop an apple crate, while belting out her hits.