Title: From Biological to Social Processes: Interdisciplinary Training in Life Course Research The poor overall health status of the US population in comparison with our high-income peers and the staggering gaps in key measures of health and well-being by socioeconomic status, race/ethnicity, and gender across the life course highlight the urgency at which we must address the factors and mechanisms that lead to poor health outcomes. At the same time, it has become ever more apparent that scientific paradigms and research approaches need to more fully incorporate the complex constellation of factors that fundamentally influence health and well-being from birth through adulthood. For these reasons, novel integrative research, from cells to society, is needed to better address the social and biological factors that cause persistent health inequalities and result in relatively poor overall levels of health in US society. This renewal application of the Interdisciplinary Training in Life Course Research (ITLCR) program proposes continuation of an innovative and exciting predoctoral and postdoctoral training program that is producing and will continue to produce highly trained interdisciplinary trainees who enter from either the social sciences or health sciences and who are trained to conduct integrative work across these areas to address some of the country’s most pressing health problems. Specifically, our program recruits promising trainees from both the social and health sciences and focuses on five critical objectives. First, our trainees gain substantial expertise in a gap area of study outside of their own discipline. Second, our trainees are immersed into interdisciplinary interactions, exchanges, and experiences that broaden their scientific proficiency. Third, our trainees learn from leading experts on how to conduct integrated biological/health-social population health research at the highest level. Fourth, our trainees are provided with a first-rate structure and culture to produce their own integrative research at the highest level. And fifth, our trainees are instructed on best practices in conducting integrated research with the highest ethical standards in mind. Our trainees develop into creative and flexible scientists who are able to develop new research pathways and create the innovative unifying frameworks that arise from crossing disciplinary boundaries. Specifically, we seek continued support for seven pre-doctoral trainees (split between the health and social sciences) and two post-doctoral trainees (one from each of the social and health sciences) for the ITLCR. Since our program began in 2017, our trainees have been exceptionally productive; we have also built a very diverse training program. With substantial guidance from the program directors and their cross- disciplinary mentors, ITLCR trainees will continue to develop individually tailored training plans in either the social sciences or health sciences, with the plan tailo...