The Houston ECHO Pregnancy Cohort Study Site - Investigation of neighborhood- and individual-level risk factors provides a framework for understanding child health. These factors affect life experiences and can induce stress, which lead to a cascade of changes in biologic function and physiological stress responses, including epigenetic processes. Hence, both upstream and downstream factors coalesce to influence children’s health, including neurodevelopmental and respiratory health, which are both widespread and largely unexplained by individual-level risk factors alone. Exposure to toxicants (a downstream factor) has been implicated in children’s neurodevelopmental and respiratory health. Thus, in Aim 1, we propose to elucidate profiles of exposure to chemical mixtures during the prenatal and postnatal periods that impair neurodevelopmental trajectories and assess whether these effects are modified by prenatal stress. In Aim 2, we propose to characterize features of the neighborhood and will evaluate the potential role of toxicant exposures and epigenetic aging as mediators of the relation between the neighborhood and child neurodevelopment. In Aim 4, we will explore the association between preconception exposure to second- and third-hand tobacco exposure and children’s respiratory health outcomes. Our ECHO Cohort Study Site (Aim 3) will enhance the ECHO Consortium with the recruitment of study participants from Houston, Texas, the fourth largest city in the nation that is located in a region for which there are currently few participants in ECHO. Hence, the addition of participants from our Study Site will strengthen the ability of the ECHO Cohort to address research questions related to children’s health. We will leverage infrastructure from our parent institutions, provide mentoring to early- and mid-career investigators; and work collaboratively and synergistically with other cohorts to ensure success of the Houston ECHO Pregnancy Cohort site.