Increasing diversity in engineering, which is a goal of the profession, education and government, starts with increasing the diversity of those choosing to study the discipline. This paper focuses on girls' engagement in engineering. Data is from a survey of girls attending a university open day and interviews with practising female engineers. The notion of "possible selves" is used to explain patterns in their responses. Both prospective and participant groups indicated that family, friends, teachers and societal messages informed and influenced their view of what engineering involved and who could be an engineer. Practising female engineers identified the impact of school subject choices, 'hands-on' and practical home experiences and the nature of the lecturer and peer support. This paper contributes to discussions of when and how to encourage girls into engineering, offering evidence that a comprehensive approach is needed that includes the community, schools and tertiary institutions as well as the profession.