(ABC News) -- Michelle Obama, wearing a custom Jason Wu ruby-colored chiffon and velvet gown, with a halter-top neckline and deep back, stunned again Monday night at the inaugural balls.
The first lady also wore a Wu gown -- a floor length, one-shouldered white number -- to the inaugural balls four years ago, taking the 26-year-old designer to instant celebrity.
She chose Wu again for this year's inaugural, much to his shock, Wu said, embellishing his creation with a handmade diamond ring by jewelry designer Kimberly McDonald and Jimmy Choo shoes.
Wu wasn't the only one surprised. Obama's choice also astonished a number of fashion critics, who thought she'd choose another little-known designer.
Wu was born in Taiwan, grew up in Canada and was educated in the United States, Tokyo and Paris. Now based in New York City, more than 85 percent of the Jason Wu Collection is made in New York's Garment District, according to Jason Wu Studios. Made-in-New York might have been a selling point, as the first lady tends to favor American designers.
Wu said he hadn't known that Obama had chosen his design again, although he did create it specifically for her and submitted the sketches and finished gown to the White House. It was quite a shock to him when she walked onto the stage at the Commander-in-Chief's Ball Monday evening.
"Mrs. Obama likes to keep her secrets. She surprised me again. She's really good at it," Wu told Women's Wear Daily after she took the stage. "I was so nervous. You'd think I wouldn't be, since I'd experienced it before, but I really was."
Women's Wear Daily reported that four years ago, when Michelle Obama entered the ball wearing his gown, Wu had only three employees and was at home eating pizza with a friend. This time he was watching with a team of 30 in his downtown New York City studio.
"I was just elated. It's hard to describe," he told WWD.
And of dressing Obama in the bold red?
"Like last time, I had to go with my gut. I instinctively had to think of the woman in the dress. After four years in office, I thought the country was ready to see a confident first lady in red. It just felt right," he said.
On Monday evening, Wu also spoke with The New York Times, and said he was "still floating."
"You have to think about the client, and I felt like red was such a perfect color for her. It's such a confident color for her. and it really was my first instinct," Wu told the Times.
After the first lady took the stage Monday night with the president, they danced to Al Green's "Let's Stay Together," performed by Jennifer Hudson. Obama's gown and the accompanying accessories will go to the National Archives.
Political fashion stylist Lauren Rothman told ABC News she wasn't surprised that Obama chose Wu instead of putting the spotlight on another little-known designer.
"There was a lot of pressure on who was going to design that ball gown, but deciding on Jason Wu took some of that pressure away," Rothman said, noting that Obama wore Reed Krakoff to the official ceremony and Thom Browne at other inaugural events, which will undoubtedly boost their careers as well.
"I am not at all surprised that she was loyal to Jason Wu, because she is loyal to the people she wears," Rothman said. "I don't know if anyone could have imagined that she would have worn him again, but at the same time, it's not surprising because her fashion personality is very loyal."
Rothman also believes the choice signaled assurance, saying, "In the second term she is sending a message that she's got a more relaxed, quiet confidence in what she has to prove fashion-wise."
Obama does wear Wu quite often; the young designer is one of her favorite choices. She wore a magenta sleeveless dress of Wu's for the cover of Vogue in March 2009, and she wore a black-and-white sheath dress by Wu in a 2008 interview with ABC's Barbara Walters. Wu and Obama were originally introduced by Vogue's Andre Leon Talley.
Wu has won several awards for design, including the Swarovski Award for Womenswear at the CFDA Fashion Awards in 2010. In 2011 he was nominated for the CFDA/Swarovski Award for Accessory Design and in 2008 was named one of the finalists in the CFDA/Vogue Fashion Fund. He launched his first ready-to-wear line in 2006, at the age of 23.
Last year Wu designed a line for Target, which sold out almost instantly.