During the past 20 years, the afterschool field has been held accountable in varying ways--first, on the ability to provide safe places for young people to spend time while their parents work; then, on success in helping to improve participants' academic achievement as a supplement to the school day. Today, measuring success in afterschool programs is more nuanced and has been influenced by an increased recognition that the social and emotional competencies youth develop while in afterschool programs are also critical to their success in school and life. This first brief in our series, "Beyond the Bell: Research to Practice in the Afterschool and Expanded Learning Field," focuses on how afterschool programs contribute to the development of social and emotional competencies in young people. In practice, we see how high-quality programs can help participants learn, grow, and develop. But what does the research say? How can we prove it? We chose to focus our first brief on this important topic because there has been a growing recognition that afterschool programs can and do facilitate the social and emotional development of young people. Despite the recent attention this topic has received, efforts to define and measure social and emotional competencies in afterschool settings are still emerging. This brief provides an overview of work done to date both in afterschool and school-based settings to define social and emotional learning, shares recent research on how afterschool programs contribute to the development of these competencies, and offers some next step recommendations to both practitioners and researchers. [For Brief No. 2, see ED563829; for Brief No. 3, see ED563831; for the planning tool, see ED563832.]