When Roz Brewer signed on to Walgreens as CEO, the company knew it was getting a rock star to guide its aggressive expansion into healthcare. Brewer had already served as CEO of Sam’s Club, where she doubled the number of organic products on store shelves, and as chief operating officer of Starbucks. A breaker of glass ceilings and an outspoken advocate of racial and gender equity, Brewer brings decades of leadership experience to a company whose purpose, she says, is “to create more joyful lives through better health.” Under her sure hand, Walgreens is moving further into retail medicine, adding a rich set of store-based clinical services to its offerings and carefully tracking health outcomes.