How do young people determine what activities they value--and are good at? What motivates an individual to choose a particular career? What key factors should be addressed in interventions to enhance academic engagement? This book offers the first comprehensive presentation of situated expectancy–value theory (SEVT), a multidimensional model that has guided research into motivation and achievement for over 40 years. SEVT originators Jacquelynne S. Eccles and Allan Wigfield are joined by leading SEVT proponents to describe the model's development and unpack its constituent parts. They reflect on how their long and productive collaboration took shape; discuss lessons learned about the individual, family, school, and sociocultural factors that shape motivation; review cutting-edge methodological developments and intervention studies; and provide a vital blueprint for future SEVT research.