This chapter begins by introducing the field of bisexuality research in Europe and discussing core developments and issues in European studies on bisexual people and other people with plurisexual orientations and identities. It then provides a detailed overview of the European studies that are part of the three themes of this book: sexual citizenship, romantic relationships, and bisexual+ identities. This overview is followed by a section on terminology in bisexuality theorising to clarify a number of key concepts; this is necessary to avoid confusion as concepts may have different meanings in different disciplines or sub-fields. Finally, the chapter outlines the structure of the book.