Mad Men costume designer Janie Bryant is stepping out from behind the scenes and in front of the camera! The award-winning designer—who we love for her weekly fashion recaps of the hit show on InStyle.com—is the new face of Hearts on Fire diamonds. "In costume design, it's all about detail and inspiration, and that is why Hearts On Fire diamonds have a unique appeal for me," said Bryant. "They can change the focus of a room the same way great costume design can change the focus of a scene." And who doesn't love diamonds? See more celebrities starring in fall campaigns in the gallery.