The chapter explains the role of text production in intellectual, cultural, and social mobility in a digital age. Written communication is becoming increasingly important across the domains, where in order to produce text people must cross boundaries which are encountered neither during habitual practices of text production nor during formal education. The three boundary-crossings the chapter focuses on are (1) crossing professional domains through multi/inter/transdisciplinary text production, primarily in research settings, (2) crossing geographic frontiers through the globalization of education and work, and (3) crossing professional boundaries through personal career transitions due to unexpected changes. (This is in contrast to the studies of “lifelong learning” discussed in Poe and Scott, this volume.) The chapter emphasizes the newness of studies of boundary crossing and discusses the difficulties in formulating such studies, not least because the boundaries themselves are not totally fixed. We then outline the various theories, methods, and ideological orientations that have thus far informed boundary-crossing studies, the challenges that their problems and methods pose to applied linguistics, and some of the research needed.