Milk is the food that unites humans with the more than 5,000 other members of the Mammalia class. Milk supplies critical nutrients for newborns and is valued as a dietary component for all age groups. Expanding global trade in milk and milk components reflects an important role as a traditional foodstuff and in food product innovation. The rapidly expanding and urbanized middle class in emerging market countries is driving increased demand for milk and dairy products. The international development community and government partners are working to improve food security for vulnerable populations, including reducing high rates of malnutrition in adolescent, pregnant and nursing women and infants through diversification of diets. Milk and milk products are recognized by nutritionists as key components of diversified diets. Families grazing livestock across semi-arid lands often manage milking animals to supply milk for women and young children. In higher-potential areas, conversion of forage and crop by-products to milk and dairy products is a key income generation strategy for the poor, with women often controlling milk income. The US Agency for International Development (USAID) and other development partners recognize the potential of milk production and marketing to transform the lives of the rural poor. The Feed the Future initiative (www.feedthefuture.gov) is the US Government’s contribution to the global effort to improve income, food security and nutrition in poor households. Implemented in in Africa, Asia and Latin America and the Caribbean, Feed the Future strategies enhance household income by linking families to dairy value chains while increasing the availability, access and utilization of milk as a nutrient-rich animal-source food. Pastoralists as well as sedentary smallholder producers are assisted to increase milk-derived income as well as produce milk for home consumption. Dairy producers in emerging market countries face several challenges in an increasingly globalized dairy market: accessing technology and services; meeting raw milk quality standards; and control of production diseases, especially mastitis.