Project Zero is a research group at Harvard Graduate School of Education that has investigated learning and thinking since 1967. Their mission is to understand and enhance learning, thinking, and creativity at both individual and institutional levels. The document discusses why establishing a culture of thinking in classrooms is important for learning, retention, and understanding. It introduces thinking routines as strategies to direct student thinking and structure discussions. Examples of thinking routines are provided, like Think-Puzzle-Explore, to engage students and develop questions for inquiry on a topic. In summary, the document advocates for creating a thinking culture in classrooms to support challenging and successful student learning.