Over the past 15 years, people in low- and middle-income countries have experienced a health revolution—one that has created new opportunities and brought new challenges. It is a revolution that keeps mothers and babies alive, helps children grow, and enables adults to thrive. Millions Saved, authored by Amanda Glassman and Miriam Temin with the Millions Saved team, chronicles this global health revolution from the ground up. It showcases 18 remarkable cases in which large-scale efforts to improve health in developing countries succeeded and 4 cases in which promising interventions fell short of their health targets when scaled-up. Each case demonstrates how much effort is required to fight illness and sustain good health.