A legume is a plant from a special family that grows its seeds inside pods. When you eat green beans, peas, or peanuts, you're eating legumes. Split the pod of a snap pea and you'll find those round seeds lined up inside: that pod-and-seed combination is the hallmark of legumes.

The legume family includes foods you might not realize are related: black beans, lentils, chickpeas, soybeans, and even peanuts (which grow underground but are legumes, not true nuts). These plants have a remarkable ability that makes them incredibly important: tiny organisms living on their roots can take nitrogen from the air and turn it into fertilizer for the soil. Farmers have known for thousands of years that planting legumes helps restore tired farmland.

Legumes are nutritional powerhouses, packed with protein and fiber. For billions of people worldwide, beans and lentils provide essential protein that might otherwise come from meat. A bowl of rice and beans together gives your body complete protein, which is why this combination appears in cuisines from Mexico to India to the American South.