The idea of problem posing is not new, but it has received increased attention in light of new approaches to mathematics education. Mathematical problem posing builds on young children's natural curiosity. It promotes children's "engagement in authentic mathematical activity"; enables children to "encounter many problems, methods, and solutions rather than only one of each"; and fosters creativity. As children explore their environment, they ask and pose questions. Effective teachers recognize and provide opportunities and experiences to build math skills and concepts within that environment. One way to do this is by guiding classroom discussions about children's problem-solving experiences. This article describes how one teacher encouraged children to pose their own math problems during a five-day investigation in their classroom. Included are examples of teacher questions and children's posed problems and solutions.