Cathy Fosnot and Pam Harris team up to bring Problem Strings to a K-12 audience. The powerful teaching tool, Problem Strings, is a purposeful sequence of related problems designed to help students mentally construct mathematical relationships. It is an intriguing lesson structure during which teachers and students interact to construct important mathematical strategies, models, and big ideas. The power of a problem string lies in the carefully crafted conversation as students solve problems, one at a time, and the teacher makes student thinking visible and draws out important connections and relationships. Finally, we have a way to produce automaticity and fluency with elementary, middle, and high school students beyond just showing and memorizing steps - and get results!