As a historian, I use my research skills to address problems involving peoples and places on the margins, intending to enrich our understanding of China as a historical concept and to bridge the gap between Asia-based and Europe-based studies on common problems about social boundaries and legal borders. I have endeavored to cross the historical marks that conventionally distinguish “modern” from “pre-modern” and to traverse the existing national borders that define China’s territory. I primarily study the historical roots of contemporary problems, and particularly the problems concerning the making, shifting, and lifting of boundaries and borders in Chinese society.