Book excerpt: In recent years, the world has seen unprecedented attention and political commitment to addressing malnutrition. Milestones such as the Scaling Up Nutrition (SUN) Movement, the Lancet Maternal and Child Nutrition Series, and the Second International Conference on Nutrition (ICN2) have marked the rapid rise of nutrition on the global policy and research agenda. These developments reverse years of relative neglect for nutrition. Undernutrition is a global challenge with huge social and economic costs. It kills millions of young children annually, stunts growth, erodes child development, reduces the amount of schooling children attain, and increases the likelihood of their being poor as adults, if they survive. Stunting persists through a lifetime and beyond—underweight mothers are more likely to give birth to underweight children, perpetuating undernutrition across generations. Undernutrition reduces global gross domestic product by US$1.4–$2.1 trillion a year—the size of the total economy of Africa south of the Sahara.