The chapter defines the scope of the book and structure. The aim of the book is to characterize the dynamics of transit crime, in particular sexual harassment and violence, from the perspective of those who are most targeted by these offences, namely young people. The book focuses on women but also adopts a more holistic approach by considering the intersectionality of safety of young adults as transit passengers; it presents examples from a variety of cities worldwide, giving voices to young people from several countries in the Global North and the Global South. The chapter also introduces some of the most common terms used in this edited volume and the chapters synopsis.