Using a lifecourse epidemiology perspective, this presentation will highlight comparative analysis of birth cohorts followed into adulthood in diverse geographic and ecologic settings. Data from the Philippines, Guatemala, Brazil, South Africa, and India allow for exploration of the importance of the first 1000 days —conception to age 2 years— in shaping multiple aspects of health and well-being in young to middle adulthood, including socioemotional, cognitive and physical outcomes.