Justin Timberlake, Jessica Biel, Demi Moore, Anne Hathaway, Kate Hudson, Eva Mendes and Elton John dressed up for a night out Thursday in New York at the Cartier 100th Anniversary in America Celebration.

Demi Moore tells ET which piece of Cartier jewelry is her favorite.

"My wedding ring, my engagement ring which is a 1937 Cartier band," Demi says. "I have quite a few but that would be my favorite."

"I'm here to celebrate 100 years," Eva Mendes tells ET. "It's an amazing milestone. Obviously Cartier is just an iconic brand. Sheer elegance, synonymous with glamor, and real elegance. Yet what I love about Cartier is that they have a heart and they do so much charitable work.

The party was held at the Cartier Fifth Avenue Mansion with a display of 100 one-of-a-kind Cartier Collection creations. The exhibit will be on display in New York until May 21, and will then be moved to Cartier's Beverly Hills location on Rodeo Drive in June.

Watch the video for more from the party, and to hear the stars explain how they are trying to stay calm about the recent Swine Flu outbreak.