This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book provides an overview of regionalism in East Asia. It examines the economic effects of the integration of 16 East Asian countries in the regional comprehensive economic partnership (RCEP). The book provides an anatomy of the evolution of the structure of China’s trade with Southeast Asian countries using detailed Chinese Customs data. It analyses the impacts of association of Southeast Asian Nations's (ASEAN) free trade areas (FTAs) on trade in goods in Southeast Asia using disaggregated trade data. The book also examines in depth the uptake of FTA provisions by firms in Thailand to shed light on ongoing negotiations for the RCEP. It explains the cost of ASEAN’s rules of origin. The book conducts a quantification exercise on the effects of services trade liberalisation for the ten Asian economies, including several members of the RCEP.