The ‘first 1000 days of life’, covering conception to age two, is recognised as a critical period for the growth and development of young children. Evidence suggests that good nutrition in early life can help adults become taller, stronger, healthier, and more intelligent and, thus, more economically productive, with many benefits for the next generation as well. The concept of a ‘window of opportunity’ is essential for designing intervention strategies. However, how to promote healthy growth in the first 2–3 years, without provoking excess weight gain and adiposity, is a major challenge to public health policymakers. This chapter addresses the global burden of childhood under and over-nutrition, highlighting the main public health interventions for improving child nutrition.