This special issue of Cross-Currents focuses on the region of the Sino-Tibetan borderlands that Tibetans call Kham: a historical frontier where several spheres of authority have competed, expanded or retracted, and sometimes overlapped. It has long constituted a buffer zone between the larger political entities of Central Tibet and China proper, and is an area that crosses cultural, ecological, and political boundaries.Kham is one of three traditional divisions of the geographical space that makes up what is often called "cultural Tibet" or "ethnographic Tibet," together with the central region of Ü-Tsang and the northeastern region of Amdo (see map 1). What makes the history of eastern Tibet special, as Wim van Spengen and Lama Jabb (2009, 7) have rightly argued, is its "relative location" vis-à-vis China and Central Tibet, an in-betweenness that make it a "contingent region" (Tsomu 2015, 1), both an interface and a place in its own right. Despite evidence of the relative autonomy-or even sometimes independence-of the disjointed polities that have made up Kham throughout history, its intermediate location and relationship with the neighboring centers of power have contributed to its evolving topology.The articles in this special issue of Cross-Currents stem from a collaborative project called "Territories, Communities, and Exchanges in the Kham Sino-Tibetan Borderlands." 1 Within the framework of this research project, the authors whose work appears here have avoided naturalizing any particular definition of Kham-although it is an inescapably endogenous category. Regions are the products of contested historical and socio-spatial processes. In Kham, influences from multiple centers have been exercised with varying intensity, and belongings and allegiances themselves have been multiple and variable. As Peter Perdue (2005, 41) contended, "the frontier zone was a liminal space where cultural identities merged and Gros 2 Cross-Currents: East Asian History and Culture Review E-Journal No. 19 (June 2016) • (http://cross-currents.berkeley.edu/e-journal/issue-19)shifted, as peoples of different ethnic and linguistic roots interacted for common economic purposes." These liminal areas can be seen as "microcosms," as Nicola Di Cosmo and Don J. Wyatt (2003) have proposed, where cultures and identities are constantly recomposed. In this issue, we adopt a multipolar approach to the adaptive and intrinsically mixed properties of border areas, which goes against unitary visions of China or Tibet. In doing so, we highlight the timespecific processes that took place in the history of this frontier, especially from the eighteenth century onward.Map 1. Geographical location of Kham. Source: Created by Rémi Chaix, based on data from NASA's Shuttle Radar Topography Mission (SRTM).In order to decipher the processes that unfolded on the frontier, it is necessary to look closely at a wide range of issues, including migration, ethnic demographics, trade networks, indigenous notions of power or potency, political negotiations, political a...