Environmental exposures profoundly shape lifespan health and disease trajectories. Preconception and pre- perinatal exposure can permanently alter the developing brain and associated regulatory systems to increase susceptibility to a host of diseases and developmental challenges. Protective and promotive environmental factors can promote well-being, even amidst adversity. The ECHO Consortium of Cohort Study Sites, Cores, and Centers is dedicated to mapping the impact of early exposures on child health and development. Good science depends on good measurement. Our proposed ECHO Measurement Core will advise, orchestrate, and frame the coordinated, sensitive measurement of exposures, developmental processes, and health outcomes central to achieving ECHO's objective. We propose three aims. Aim 1 is to develop and refine measures for the ECHO Cohort Protocol (ECP), including methods to implement the measures. We will lead efforts to optimize the measurement of exposures and outcomes, mindful of best measurement practices as well as respondent and staff burden. We will lead the timely development of a preconception section for the Protocol by drawing on diverse expertise across the ECHO Network to ensure feasible, robust, and culturally sensitive assessment of critical data elements in the preconception period that have direct import for the primary ECHO child health outcomes (pre-, peri-, post-natal, airways, obesity, neurodevelopment, and positive health). We will leverage novel psychometric and technological methods such as computer adaptive tests, wearable sensors, and other innovations in remote assessment, to reduce barriers to study participation and enhance participant retention. Aim 2 is to assist the ECHO Consortium in implementing and evaluating the ECP. We will further collaborate with everyone in the Consortium to finalize the protocol and establish a standard implementation strategy that can be implemented across the diverse Cohort Study Sites, including determining optimal study visit structure and choreography, developing Manual(s) of Operating Procedures (MOPs), and creating, supporting, and, when appropriate, leading training. Aim 3 is to lead strategic decision-making and operational strategies to incorporate new and revised measures to advance ECHO Cohort science while minimizing participant and staff burden. We propose to optimize measurement decisions by maintaining collaborative communication, rapidly deploying data and biospecimen collection for time-sensitive needs, identifying and evaluating important measurement developments, creating a technology pipeline for rapid adoption of innovative approaches to data collection, and ensuring data collection strategies are validated for diverse populations. Our measurement science expertise within and outside of ECHO, paired with our participant-centered approach, enables us to bridge reliable and valid assessment with practical feasibility and ultimately allows us to bring ECHO scienti...