Temperament is a contextual and biological trait that influences how an individual interacts with the environment. Although scholars have organized and prioritized different dimensions of temperament, in this chapter we focus on temperament dimensions that are most salient to--and how they are exhibited in--early childhood classrooms. Temperament continues to be an important topic in early childhood classrooms because it is both important for children learning to manage their social emotional competence, which relates to long-term academic success and positive mental health, and for teachers to develop classroom management skills that provide a positive climate for an array of children and temperament types. After introducing the notion of temperament, we describe how teachers may create environments and react to children in ways that support child temperament. Finally, "INSIGHTS into Children's Temperament," an empirically based social-emotional intervention, will be introduced. This intervention focuses on how children's temperament unfolds in the classroom and how the adults in children's lives can create "goodness-of-fit" for optimal outcomes.