EQUAL-LIFE will develop and test combined exposure data using a novel approach to multi-modal exposures and their impact on children’s mental health and development. A combination of birth-cohort data with new sources of data, will provide insight into aspects of physical and social exposures hitherto untapped. It will do this at different scale levels and timeframes, while accounting for the distribution of exposures in social groups based on gender, ethnicity, social vulnerability. Beginning with child development and mental health, a set of theory-based questions is formulated, a wide range of relevant environmental and social hazards is defined and validated at the stakeholders end. Exposure assessment combines traditional GIS-based approaches with omics approaches and new sources of data that could explain aspects of the urban environment at a higher spatial and temporal granularity, and provide insight into untapped parameters relating to exposure (spatial quality of neighborhoods). These together form the early-life exposome. Statistical tools integrate data at different scale levels and times and combine e.g. machine learning, causal models with subgroups measures. EQUAL-LIFE uses data from birth-cohorts, longitudinal school data sets and cross-sectional studies (N=>250.000), including data on exposures, biomarkers, mental health and developmental outcomes, in their social context. EQUAL-LIFE contributes to the development/utilization of the exposome concept by 1) integrating the internal, external and social exposome 2) by studying a distinct set of effects on a child’s development and mental health 3) by characterizing/measuring/modelling the child’s environment at different stages and activity spaces 4) by looking at supportive environments for child development, rather than merely pollutants 5) by combining physical, social indicators with novel biomarkers and using new data sources describing child activity patterns and environments. EQUAL-LIFE is part of the European Human Exposome Network comprised of nine projects selected from this same call.