With crosscutting concepts such as stability and change in the "Next Generation Science Standards," this article was written for those who have wondered how to teach these concepts in a way that is relevant to students. In this investigation, students ask the question, "Why is the pond dirty?" As students investigate the health of a local pond, they become curious about science--they ask questions and develop an understanding of the complexity of the systems that make up the pond environment and how these systems affect stability and change within the pond. In this investigation, students ask questions, draw a model, plan and carry out investigations, analyze and interpret data, use mathematical thinking, and base explanations on evidence--all of which are science and engineering practices considered essential in the "Next Generation Science Standards".