PROJECT SUMMARY Media use is so common and widespread that, arguably, it is a major influence on children's development. Although the impacts of television on parent-child interaction and young children's development are well documented, little is known about how newer screen media influence these processes. Utilizing the NICHD- funded Baby Books 2 project (R01HD078547), this project describes the media habits of very young and diverse children at four time points in their early years (9, 18, 24, and 30 months), providing insights into the trajectory of media consumption for low-income, ethnically and linguistically diverse children. Importantly, we capture information about infants and toddlers' media habits with their mothers and their father as well as the types of media activities they engage in. This includes solitary use, co-use with parents, and use that is interactive or passive. Next, we identify which infant and parental characteristics predict media use over time. Finally, we test how early media exposure and use are associated with parent-child relationship quality and children's language development, social-emotional skills, and executive functioning at 24 and 30 months of age. This study is the first to use a longitudinal design, include diverse families, use mother-report, father- report and observational measures, and explore what, for how long, and with whom young children engage with digital media. Findings will offer concrete recommendations for promoting healthy media use among infants and toddlers.