How does the experience of social marginalization become physiologically embedded? This talk presents a multi-site study that investigates how systemic disadvantage "gets under the skin” to influence human biology and health. Through a community-based photovoice design, I investigate the built environment by centering the lived experiences of residents as they describe how poor water infrastructure and severe flooding influence their health, wealth, and well-being. I follow this with a quantitative analysis using structural equation modeling to identify a causal pathway linking multiple social determinants of health to changes in the gut microbiome, evaluating their direct and indirect effects on gut microbiome diversity and composition. Lasty, I will present preliminary data on the relationship between environmental contaminant exposure and obesity in these study sites. Together, this mixed-methods approach offers a holistic perspective on how systemic inequality moves from the environment into the human body.