Adolescents, comprised of 10-19 year olds, form the largest generation of young people in our history. There are an estimated 1.8 billion adolescents in the world, with 90% residing in low- and middle-income countries. The burden of disease among adolescents has its origins in infectious and injury-related causes, but nutritional deficiencies, suboptimal linear growth, and undernutrition are major public health problems, even as overweight may be on the rise in many contexts. Summary and Key Messages: Girls are most vulnerable to the influences of cultural and gender norms, which often discriminate against them. Dietary patterns and physical activity, in addition to schooling and countervailing social norms for early marriage, influence health and nutritional well-being of adolescents. Nutrient requirements - -including those for energy, protein, iron, calcium, and -others - increase in adolescence to support adequate growth and development. In settings where dietary intakes are suboptimal, anemia and micronutrient deficiencies are high. Endocrine factors are essential for promoting normal adolescent growth and are sensitive to undernutrition. Growth velocity increases during puberty when peak height velocity occurs and catch-up is possible; in girls, about 15-25% of adult height is attained. A premature pregnancy can halt linear growth and increase the risk of adverse birth outcomes. Research is needed to fill the huge data gaps related to nutrition and growth during adolescence, in addition to testing interventions during this second window of opportunity to enhance growth and development, improve human capital, and to end the intergenerational cycle of growth failure.