New York’s Fashion Week is already in full swing and Hollywood’s biggest stars have been making their presence known! On Friday, Jessica Biel was the host for the Dior and Saks Fifth Avenue dinner celebrating the brand’s Fall/Winter 2013 prêt-à-porter collection now available at the Fifth Avenue department store. Inside, the entire third floor was transformed into a hall of mirrors to showcase the winter collection along with inflatable mirror balls and live runway footage of the collection displayed on TV screens. The brand also took over Saks’ front window displays with visual installations that were inspired by the collection and custom made for the store. Guests included stylist and designer Rachel Zoe and her husband Rodger Berman, along with Ashley Madekwe, Maria Sharapova and more. Click through the gallery to see more stars from this week’s hottest fêtes!

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See Jessica Biel’s Transformation 
Get an Exclusive Look Inside Rachel Zoe’s Home
Everything You Need to Know About Fashion Week