Increased investment is urgently needed to address evolving health risks and meet the mental and sexual and reproductive health needs for the nearly 1.3 billion adolescents (aged 10-19 years) globally, according to a new scientific publication released by the World Health Organization (WHO).  Adolescence is a unique and critical stage of human development, involving major physical, emotional, and social transitions, and is a pivotal window for laying long-term foundations for good health.