Millions of people in East and Southern Africa (ESA) remain at high risk of food insecurity. The main causes include poor crop productivity, soil nutrient deficiencies, erratic rainfall, and unsustainable farming practices. Maize is the major food crop and occupies large land areas. Many people’s diets are heavily dependent on maize, which is produced inefficiently with little fertilizer, resulting in low yields. Maize is also lacking in essential nutrients, putting farming households at risk of nutrient deficiencies. Grain legumes are grown mainly for their high-protein seed, which provides a more nutritious diet than maize, and includes important macronutrients (proteins, fats, and dietary fiber), and essential micronutrients (vitamins and minerals). Grain legumes also obtain nitrogen from the air and accumulate it in the plant via a process known as biological nitrogen fixation, which takes place in the nodules on their roots (Figure 3.1).