Youth antisocial behavior, which includes violence, rule-breaking, and substance use, represents a major public health concern because of the negative economic, social, and health effects it has on perpetrators, victims, and families. To better understand its developmental origins, we need to improve our characterization of the heterogeneity within antisocial behavior. My talk will focus on a dimension within antisocial behavior defined by high levels of callous unemotional (CU) traits, which comprises low empathy and guilt and a lack of caring about others, and predicts particularly severe and chronic aggression and rule-breaking across development. I will present research examining the origins of CU traits, focusing on early childhood given that this developmental period heralds the emergence of individual differences in empathy, guilt, and conscience. My work evaluates the meaning and measurement of CU behaviors in early childhood and their role as a developmental precursor to CU traits and severe behavior problems later in childhood. I will also present findings from my work examining the importance of context and the environment to the development of CU behaviors, with a particular focus on parenting practices. The talk will conclude with a summary of my recent research modeling the interaction of context and biology over time and how specific environmental, neural, and genetic risk factors interact to increase the risk that children develop CU behaviors and more severe antisocial behavior.