Tiffany & Co. hosted its 1920s-themed Blue Book Ball in NYC last night, which in turn inspired a seriously glamorous attendance list. Falling in line with the brand's theme and signature color, Kate Hudson stunned in a strapless, Tiffany-blue Reem Acra Resort '13 gown and sparkling diamond earrings. Gwyneth Paltrow opted for a cooler blue hue, wearing a long-sleeved Ralph Lauren gown with a jeweled butterfly brooch, and Jessica Biel showed off her love for Spring prints in a gorgeous floral-patterned Elie Saab gown and diamond-crusted hair brooch. And that's just the beginning. Click through the slideshow to see the rest of the chic celeb pack — including Sarah Jessica Parker, Carey Mulligan, and Michelle Williams — along with a behind-the-scenes glimpse at the swanky party scene inside.