This chapter summarizes research on digital media, cognition, and brain development throughout childhood. Rapid brain development produces age-related differences in children’s responses to media and the potential impact of media on cognition. In infancy, cognitive constraints limit whether and how infants learn from media, although they learn under some conditions (e.g., with repetition or parental scaffolding). Throughout early and middle childhood, children use a wider range of media and become better able to comprehend and learn from media. There is an emerging literature suggesting associations between screen time and brain structure in children; however, brain-behavior associations are not well understood. Meta-analytic reviews of research on media and cognitive development report mostly nonsignificant or small negative associations between overall screen time and cognitive outcomes (e.g., self-regulation, attention, language, academic achievement). However, there is substantial variability across studies and individuals, with media effects varying by the content and context of media use. For example, solitary media use (versus parent-child joint media engagement) and use of noneducational or adult-directed content (versus child-directed informational content) are associated with more negative and fewer positive outcomes. This chapter concludes with a future research agenda and recommendations informed by the current literature.