The introduction provides a brief overview of the development of the Irish juvenile justice system, highlighting the lack of legislative and policy development throughout most of the twentieth century. It introduces the reader to the key legal and policy developments including legislation underpinning the reformatory and industrial school system, the Children Act, 1908, the Children Act, 2001 and the development of the Irish Youth Justice Service. It also explains how the book adopts a governmentality approach, examining the development of juvenile justice in Ireland from four separate perspectives: how the system itself became visible, in terms of its underlying rationalities, in terms of the technologies of government and finally in the context of the forms of childhood identity employed to govern. It finally provides a brief outline of the book itself.