Parties! The style, stars and scoop from Hollywood's hottest events

Kate Hudson, Demi Moore and Jessica Biel helped famed jeweler Cartier mark its 100th anniversary in America at the brand's Fifth Avenue mansion in New York City. While the crowd ogled pieces from the Cartier archive—on display under glass and heavy security—celebrity guests had the pleasure of wearing the precious gems. "My dad gave me my first diamond," reminisced Hudson, who accessorized her Rachel Roy cut-out dress with a stunning onyx and diamond panther necklace. "It was a tiny, tiny little chip!"

—Alyssa Giacobbe