Beyoncé's GRAMMYs Dress Designer Dishes The Details On Her Raunchy Frock

Get the lowdown on Beyoncé's 'nude illusion' GRAMMYs gown, as it's revealed she wore it before it hit the runway...

Only Beyoncé could snap up a designer gown before it hit the runway, but we all knew there was something extra special about her GRAMMYs 2014 frock.

The Drunk In Love singer dominated red carpet proceedings at last week's ceremony, with the help of Michael Costello's 'nude illusion' number. That's when she wasn't heating up the stage with Jay Z.

Now, Project Runway's Michael Costello has dished ALL the details on the breathtaking dress that had the Internet swooning (including the size tag).

'It was incredible! We didn't have any of her sizes or measurements,' the designer told the LA Times. '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 [Beyoncé's stylist] knew it was going to fit.'

'At first I was a little concerned with the pieces I gave,' he added. 'Maybe it needs to be smaller or bigger? When you send something to Beyoncé, you're just a little concerned, but Ty knew. Ty knew the fit.'

But it was all go behind the scenes as Costello and his team rushed to actually finish the frock before Bey hit the red carpet. 'The neckline, the back, the hemline was not complete, and we still had to do some of the hand sewing on it.'

Yikes. It's a good job the pros put in an extra day's work to ensure the Winter Wonderland-inspired gown covered Beyoncé in all the necessary areas. One ladylike leaf out of place could've changed everything, after all.

Got a tablet? You can now download Marie Claire magazine straight to your iPad, Kindle (just search the store for 'marie claire magazine'), Nook or Google Nexus.