There has been limited consideration of teenagers (defined as 12-19 year olds in this work) as participants and end-users in Child-Computer Interaction and mainstream HCI communities. Teenagers reside in a fascinating and dynamic space between childhood and adulthood, and working more closely with teenagers within HCI may bring great insights and benefits. This paper provides an overview of teenage development from a psychological perspective, and then reviews existing work considering teenagers within HCI. Teenagers have long been identified as unique and studied within the field of developmental psychology, and the overview we provide in this paper highlights key understandings that should be carefully considered when working with teen participants. The paper concludes by presenting a set of key research questions that need to be explored in order to effectively work with teenagers within the field of HCI and provide a roadmap for future research within the Teen-Computer Interaction area.