More than any other aspect of human development, global health has benefited from scientific and technological breakthroughs. Unfortunately, many of these breakthroughs have not reached the people most in need, at the scale and form that are required. While overall health outcomes in low- and middle-income countries have improved over the past three decades, they lag the rest of the world in virtually every single metric. People living in tropical countries—particularly in South Asia and sub-Saharan Africa—are exposed to a far greater array of health hazards than those living in other regions. By implication, these populations need access to the most powerful solutions. Yet, they have the least access to them.