This book is a result of the thematic research project at Academia Sinica “Culture, History, and State Formation: Creating Minority Nationalities in Modern China” (2015-2017) led by Wang Mingke and Max K. W. Huang. The title “Hidden People” indicates the culturally diverse and border-crossing groups that are often invisible within a unified polity with well-defined boundaries. The interactions among these peoples nevertheless have shaped the complicated process of state formation in modern China. The book is dedicated to three main themes: the construction of ethnic boundaries and nation-state in modern China; the non-Han Chinese perspectives; and the modern transformation of Islam in China. Bringing together up-to-date research by scholars from mainland China and Taiwan, this volume combines macroscopic observations and substantial case studies, and sheds light on the questions of nation building, ethnic boundary, and identity.