Organized activities (including afterschool programs, extracurricular activities, sports, community service, summer camps, and other activities outside of the regular school day) account for a significant segment of children and adolescents' lives. These activities often provide hands‐on, child‐driven experiential learning that often involve youth working collaboratively with peers. Although research on organized activities is comparatively recent, it suggests that these types of activities support the development of self‐direction, initiative, teamwork, and emotional skills, as well as cognitive and academic skills. In this chapter, bioecological and sociocultural theories are used to guide our understanding of organized activities. Methodological strategies and common assessments used to study organized activities are reviewed. Key parameters and processes, including dosage, type of activities, and program quality, are described. We consider individual, family, peer, and school/community factors that predict participation in organized activities. We also evaluate evidence of links between organized activities and child developmental outcomes. Finally, youth experiences and outcomes associated with unsupervised settings are juxtaposed to experiences and outcomes found in organized activities.