Jason Wu speaks out on Michelle Obama's gown

(CBS News) Four years ago, Jason Wu became an overnight sensation when First Lady Michelle Obama chose a gown designed by Wu for her husband's first inauguration.

Monday night, the first lady celebrated the president's second term and wore another of the designer's creations to the inaugural balls.

The designer shared the experience of discovering that Michelle Obama chose his red gown and said he was still shocked the second time.

"I was still at my studio designing the fall collection that I'm presenting in less than three weeks," Wu said Tuesday on "CBS This Morning." "So I was actually with my team, which was really nice."

"When I saw it, I was just floored," he said. "I just couldn't believe that she chose me for the second time ... I am so proud of it."

Wu explained the process behind designing a gown fit for a first lady. "I sent a couple sketches but we only made one dress. Red was what came to my head right away ... As a designer I always have to trust my instincts."

He said that the second time, the process was more collaborative between his team and the White House.

"Last time, she didn't [make suggestions], but this time I said, 'I think red is a really good color' and they said, 'Well, Mrs. Obama thinks red is a good color too ... I guess we were in sync from the beginning."

"We worked pretty closely with the team to perfect the dress," Wu said, "There [were] a lot of back and forth trips ... it took a couple of months."

Wu called the months-long effort, "a wonderful process to be able to work on it and put so much into a dress that is a part of history."

The 30-year-old designer, who has only been in business for about six years, and said it has been "amazing to have that exposure" and expand his brand in time since the first lady wore his design to the inaugural balls four years ago.