This Special Issue showcases some of the latest and best research in an important emerging field, developmental social neuroscience, which is focused on the nature and development of the mechanisms involved in socially relevant human behavior. Recent work on the neural correlates of empathy, prosocial and antisocial behavior, and inter-personal communication, for example, is transforming our view of human development by revealing complex interactions among genes and environment, including culture, that are shaping brain and behavior throughout life. This work, like research in social neuroscience more generally, is also causing scientists to reassess longstanding assumptions about the meaning of constructs and (false) dichotomies such as cognition versus emotion, and behavior versus brain. What emerges is a more holistic view of human beings as dynamic, multidimensional phenomena that are simultaneously cognitive and emotional, behavioral and neural, social and individual, depending on how you approach the phenomena and how you measure them.A prominent feature of this new research is the use of multiple methods in order to make measurements at multiple levels of analysis. What distinguishes the studies included here from other recent work in social neuroscience is the adoption of a developmental approach. From a developmental perspective, human beings are viewed as dynamic organisms, continually in flux; an effort is made to document the ontogenetic time series. The hope is that a developmental approach will provide a more comprehensive—and hence, more complete—description of human social function; namely, one that includes an understanding of the actual causal mechanisms by which this function emerges.