This supplement brings together papers focusing on the critical 1000 days of human development from pregnancy until 2 years of age. It is the third in an annual series first published as a Special Supplement of the Food and Nutrition Bulletin in June 2009. Diets of poor nutritional quality during pregnancy, infancy and early childhood lead to nutrient intakes, which do not meet requirements. This, combined with frequent infections during early childhood, results in deficits in growth (stunting), limited psychosocial development, increased risk of mortality, and reduced learning capacity and productivity later in life among those that survive. Programmes need to prevent these deficits by improving maternal and child nutrient intake in addition to preventing and treating infections.