Natalie Portman Color Blocks at the BalletS

Can anyone tell me what those bumps on the dress are? I'm taking guesses!

NEW YORK, NY - SEPTEMBER 19: Natalie Portman attends New York City Ballet 2013 Fall Gala at David H. Koch Theater, Lincoln Center on September 19, 2013 in New York City. (Photo by Jamie McCarthy/Getty Images)