Lesson study is a popular professional development approach in Japan whereby teachers collaborate to study content, instruction, and how students solve problems and reach for understanding in order to improve elementary mathematics instruction and learning in the classroom. This book is the first comprehensive look at the system and process of lesson study in Japan. It describes in detail the process of how teachers conducted lesson study--how they collaborated in order to develop a lesson, what they talked about during the process, and what they looked at in order to understand deeply how students were learning. Readers see the planning of a mathematics lesson, as well as how much content knowledge the teachers have. They observe students' problem solving strategies and learn how Japanese teachers prepare themselves to identify those strategies and facilitate the students' discussion. Written for mathematics teachers, educational researchers, school administrators interested in teachers' professional development, and professional developers, this landmark volume provides an in-depth understanding of lesson study that can lead to positive changes in teachers' professional development and in teaching and learning in the United States.