Chapter 1 provides an overview of screen time concerns reported in the media and research, with consideration of relevant learning and interaction theories which indicate that face-to-face social interaction, talk and play are essential for the linguistic and cognitive development of children. This chapter also revisits the fundamental multimodality of face-to-face interaction. The shift from face-to-face to online multimodal interaction therefore requires users to make complex linguistic and interactional adaptations to be able to achieve understanding and affiliation with interlocutors in online contexts, as occurred with the advent of the telephone. This is especially true of the most common form of online interaction, text chat, which is a unique hybrid form of social written interaction, with its own specific affordances and constraints for children’s social and linguistic development. This chapter presents key interactional differences between face-to-face and written online interaction, based on conversational resources available (or unavailable) to users in either setting, including videogame settings. This discussion provides a necessary basis for investigation of children’s written interaction in subsequent chapters.