I will describe a microsimulation model of the early life-course, which can be used to test policy scenarios around improving child wellbeing. The model focuses on the development of three outcomes: obesity, depression, and school attainment, and uses estimates from meta analyses to determine the strength of associations between factors experienced in childhood and the development of the outcomes. An app visualising the model has been designed in the R web application SHINY. The app allows policy makers and analysts to run realistic simulations in which the effects of changes in children’s circumstances are modeled. I will demonstrate how the app can be used to test scenarios, with a particular focus on interventions for obesity.