The book, the tenth volume in the series of yearbooks by the Association of Mathematics Educators in Singapore, comprises 14 chapters written by renowned researchers in mathematics education. The chapters offer mathematics teachers a cache of teaching ideas and resources for classroom instruction. Readers will find various task design principles, examples of mathematical tasks used in classrooms and teaching approaches to implement the tasks. Through these discussions, readers are invited to reflect and rethink their beliefs about mathematics teaching and learning in the 21st century, and reexamine the tasks and activities that they use in the classroom, in order to bring about positive impact on students' learning of mathematics.This book contributes towards literature in the field of mathematics education, specifically on mathematics instruction and the design of mathematical tasks and activities.