Child undernutrition is a major public health challenge, estimated to be responsible for 2.2 million annual deaths. Implementation of available interventions could prevent one-third of these deaths. Emerging evidence suggests that breast-feeding can lead to improvements in intelligence quotient in children and lower risks of noncommunicable diseases in mothers and children decades later. Nonetheless, breast-feeding and complementary feeding practices differ greatly from global recommendations. Although the World Health Organization recommends that infants receive solely breast milk for the first 6 months of life, only about one-third of infants in low-income countries meet this goal, just one-third of children 6 to 24 months old in low-income countries meet the minimum criteria for dietary diversity, and only one in five who are breast-fed receive a minimum acceptable diet. Although the potential effects of improved breast-feeding and complementary feeding appear large, funding for research and greater use of existing effective interventions seems low compared with other life-saving child health interventions.