The discount retailer is at a crossroads: how to transition from the big-box era that propelled it to the world’s largest company, to one in which customers are fussier about what they eat and can easily comparison shop thanks to the internet. In 2014, under new CEO Doug McMillon, Wal-Mart’s U.S. finally broke a nearly two-year streak of growth-free quarters on the comparable sales front. But that recovery is tenuous: it is still struggling to get people into its stores, and it has suffered from out-of-stocks and customer service that many find wanting. Last year saw a lot of turmoil: it replaced the CEO of its $288 billion U.S. division and lost its chief merchant. But the company has made strides in improving the quality of fresh food in its stores—about 55% of revenue comes from grocery. Its e-commerce investments are paying off too. Still, Wal-Mart is grappling with ever more aggressive rivals like Target and Amazon, the proliferation of dollar stores and a desire for healthier grocery offerings, meaning 2015 is a key year for McMillon to prove he can modernize Wal-Mart.