How do children, adolescents, and young adults get on track to have successful lives and how can policies help them get there? The Social Genome Project (SGP) asks these questions using a tool called the Social Genome Model: a data-rich model stretching from birth to middle age that allows analysts to examine how circumstances and actions at developmentally significant life stages reverberate through a person’s life. The model is ideal for asking “what if” questions about factors that promote or impede future success. This User’s Guide explains the root data sources, how the model works, model benchmark and validation procedures, and the advantages and limitations of the model.