This report examines nutrition, providing a fresh perspective on a rapidly evolving challenge. Despite progress in the past two decades, around 200 million under-fives suffer from undernutrition. Adding to this toll is rising obesity, which affects 38 million children. All these forms of malnutrition threaten children's development, while obesity is creating a lifelong legacy of disease. At the heart of this evolving challenge is a global shift towards modern diets that do not meet children's nutritional requirements. The report provides unique data and analysis of malnutrition in the 21st century and outlines recommendations to put children's needs at the heart of global and national food systems.