Project Viva Cohort Overview ( 170 words) The Project Viva cohort is a prospective, pre birth longitudinal study that enrolled 2,128 pregnant women (and their offspring) at routine prenatal visits in eastern Massachusetts between 1999 and 2002. Initiated by Dr. Matthew W. Gillman and colleagues at Harvard T.H. Chan School of Public Health (with NIH funding), the cohort was designed to investigate how maternal diet, environmental exposures (e.g., air pollution, chemicals), and psychosocial factors influence health trajectories from gestation through adulthood. Participants underwent in person examinations during early and late pregnancy, at delivery, and repeatedly throughout childhood (infancy, early childhood, mid childhood, adolescence) and now into young adulthood. The dataset includes detailed questionnaires, dietary recalls, medical record abstraction, anthropometry, neurodevelopmental testing, and a rich biorepository (maternal/infant blood, urine, placenta, nasal epithelium). Project Viva serves as a platform for studying developmental origins of obesity, cardiometabolic disease, asthma/atopy, neurocognitive outcomes, and intergenerational health. Its strengths lie in the pre birth enrollment, comprehensive exposure assessment, multi time point phenotyping, and integration with the larger NIH ECHO network, making it a valuable resource for epidemiologists, clinicians, and policy makers exploring early life determinants of health.