Young people's use of technology has been extensively explored in the literature. However, there has been less work theorising their technology-enabled behaviours, integrating understandings of adolescence into explanations of technology use. The study reported here begins to address this gap. It explores the digital lives of 15 young women in the United Kingdom over one year, using the tools and conceptual categories of social cognition in novel ways. An adaptation of Valsiner's Zones makes it possible to offer an account of technology use which avoids romanticism and pessimism, and enables us to: (i) recognise choice and agency; (ii) articulate technology-mediated development across disciplines and paradigms; and (iii) locate physiological development within the broader social, psychological and socio-technical realms. The paper concludes by applying the adapted framework to a single case, Megan, illuminating unresolved issues for future studies and theorising technology as shaping, rather than defining, adolescent perspectives, behaviours and relationships