Those who tuned into the Grammy’s on Sunday night were floored by Beyonce’s recent weight loss, and her gown designer Michael Costello is now revealing how shocked he was to find out she’s a size 2.

The former Project Runway contestant talked about one of the biggest stars in the world wearing his white, lace design and said since he didn’t have any of her measurements, the gown she wore was sample size.

Costello told E! News, "It was incredible! We didn't have any of her sizes or measurements. The dress was just made to fit a sample mannequin. It's smaller than a size 4. She is tiny! That dress is at least a 2/4. She looks amazing. I just love the way it all came together. Ty [her stylist] knew it was going to fit."

He added the dress was “inspired by New York. The Winter Wonderland in New York” and will be seen at New York Fashion Week as part of his collection called Winter Wonderland.

Meanwhile, Beyonce opened the Grammy’s with her husband Jay Z, singing their hit “Drunk in Love.” She was wearing a much more revealing outfit for the performance.

image: CBS