This book chapter aims to summarise Professor Leung’s major contributions that includes five aspects: (1) examining East Asian students’ success in mathematics from a cultural perspective, (2) identifying characteristics of mathematics classroom teaching in East Asia, (3) exploring the features of East Asian teachers’ mathematics knowledge for teaching, (4) investigating how language impacts mathematics learning, and (5) examining how student learning across sub-cultures may vary, to illuminate his profound influence of culture on mathematics learning and teaching. It is then followed by the summary of thirteen book chapters.