Developing Thinking in Geometry integrates pedagogy and subject knowledge to enable teachers and support staff to experience and to teach geometric thinking to pupils aged seven to 16 years. A variety of tasks will show how all learners can engage in successful geometric thinking. The book draws on pedagogic constructs developed at The Open University's Centre for Mathematics Education by a team of mathematics educators with a 20-year track record of innovative and influential approaches to teaching and learning geometry. This book is the course reader for the Open University course ME627 Developing Geometric Thinking.