Zac Posen Reveals Details of Claire Danes' Glow-in-the-Dark Met Gala Gown

— -- Claire Danes was the belle of the 2016 Met Gala in a Cinderella-like gown that was glow-in-the-dark.

The dress’ designer, Zac Posen, revealed today that it was powered by LED lights and made with fabric custom-ordered from France.

“You’re looking at light traveling vertically,” Posen said today on “Good Morning America” of the dress’ optical illusion.

Posen said the dress list up thanks to LED lights and the power of 30 battery packs. Despite its ball-gown size and its technology, the dress was not too heavy for Danes.

“The dress is hollow inside,” Posen said. “It’s as light as possible.”

The dress perfectly fit the theme of this year's Met Gala, “Manus x Machina: Fashion in an Age of Technology.”

“I’m interested in that place, where the past and the future meet, because that’s universal and that hits a cord around the world to women and girls and men,” Posen said. “Just recognizing beauty and a magic moment and fantasy and technology.

“Claire was our Cinderella,” he added.

Posen attended Monday night’s gala with Danes, his personal friend since they were both teenagers, and said they had a “blast.”

The designer said he draped the dress about four weeks ago, going into his studio and turning on his boombox to create what would become the prestigious gala’s most-talked about dress.

“I like to make people dream,” Posen said. “That’s my job.”

Posen's collaboration with Danes was also a hit on social media, kicked off by Posen's own tweet previewing the dress.