Adult learning is essential in schools. Learning Forward's Scholar Laureate Shirley Hord observes, "The improvement of our schools seldom results from mandates. What has become very clear is that change (its adoption and implementation) cannot occur without the provision of ongoing and long-term learning for the professionals" (Hord, 2011, p. xv). Professional learning communities make sense. As a structure, the premise of these communities promised a lot to the profession. However, some communities have proven disappointing, and the concept as a whole is in danger of fading like many initially exciting structures for change, such as small schools and block scheduling. Structures need substance to succeed. Substance comes from a set of design principles related to what people do within the structure, and why and how they do what they do. It is tempting to think that real professional learning communities--communities in which people really learn--can be organized from the outside or that starting them is a matter of five easy steps. The implication is that there is a right way to work toward a right outcome (and, conversely, a wrong way and a wrong outcome). This article discusses five principles of effective professional learning communities: (1) Professional learning communities emerge from passion and purpose; (2) Professional learning communities are sensitive to the environment; (3) Professional learning communities are a result of relationships; (4) People in professional learning communities acknowledge a variety of solutions and processes; and (5) Professional learning communities energize thinking.