This introductory chapter offers a brief account of the history behind this book, which originates in the MIME project, where ‘MIME’ stands for ‘Mobility and Inclusion in Multilingual Europe’. This project, which was funded by the European Commission’s Directorate-General for Innovation and Research as part of the DG’s seventh Framework Programme, presents an exceptional degree of interdisciplinarity. A dozen different disciplines from the social sciences and humanities were involved, with a total of 25 participating teams from 16 different countries. The project’s analytical framework, which federates the inputs from these various disciplines, rests on the concept of trade-off – in this case, between two desirable, but non-converging goals, namely ‘mobility’ and ‘inclusion’. This general introduction shows how the trade-off can be used as a structuring device to approach the ‘multilingual challenge’ confronting Europe and its citizens, before describing the main thrust of each of the subsequent 25 chapters. The findings presented here, which go beyond the results provided in the MIME project outputs, aim to make this interdisciplinary experience available to a wide readership of scholars.