We established Project Viva to examine the extent to which exposures and experiences during early life may affect health outcomes, including cardiovascular disease (CVD)-related outcomes, over the life course. We recruited pregnant women at their initial prenatal visit in eastern Massachusetts between 1999 and 2002. Exclusion criteria included multiple gestation, inability to answer questions in English, gestational age above 22 weeks at enrollment, and plans to move away before delivery. We conducted in-person visits with mothers during the first (median 9.9 weeks of gestation) and second (median 27.9 weeks) trimesters of pregnancy, and with both mothers and their children during infancy (median offspring age 6.2 months), early childhood (median 3.3 years), mid-childhood (median 7.7 years), early adolescence (median 12.9 years), late adolescence (median 17.5 years), and young adulthood (median 21.9 years; ongoing). We collected information on sociodemographics and lifestyle behaviors from mothers via interviews and questionnaires, performed anthropometric assessments, and collected biosamples in children. Key findings include associations of early life exposure to unhealthy lifestyle behaviors (e.g., poor diet quality or smoking during pregnancy, short breastfeeding or sleep duration in infancy), unhealthy metabolic milieu (e.g., prepregnancy obesity, excessive gestational weight gain, gestational diabetes), environmental toxicants (e.g., per- and polyfluoroalkyl substances, toxic metals), and/or adverse environments (e.g., residential air pollution, neighborhood disadvantage) with various CVD-related outcomes (i.e., greater adiposity, higher blood pressure, earlier pubertal development, and higher metabolic risk score) in children and adolescents. The ubiquity of these exposures makes this area of inquiry of considerable public health importance with regard to primordial prevention of CVD.