Cognitively Guided Instruction (CGI) is a teacher professional learning program that supports teachers to understand research knowledge of children’s mathematical thinking and how to use students’ mathematical thinking to guide instruction. CGI is a student-centered approach to teaching math with understanding. Teachers start with what their students already know and building on their understanding of mathematical ideas and their intuitive approaches to problem solving. CGI is not a curriculum or a teaching program but rather a way of listening to students, asking smart questions, and engaging with their thinking. CGI teachers are constantly working to uncover and expand every students’ mathematical understanding.