Studies have shown that heat sharply increases the amount of toxic BPA leached from plastic — right into your food. Simply put, using plastic containers and bags to store (or reheat) hot leftovers is a very bad idea. Glass storage containers, on the other hand, are a great idea: They protect them from a moldy fate. Plus, they’re perfect for reheating. These attractive, stackable containers from Anchor Hocking come with tight-fitting, BPA-free plastic lids. $10–$30 at Target.