The "Next Generation Science Standards" ("NGSS") challenge prevalent beliefs that young children are "not ready" to understand natural selection, introducing core aspects in grades 1, 2, and 3 (NGSS Lead States 2013). The authors' research and teaching team engaged in a multiyear project to understand how early grades instruction can support a learning progression toward full understanding of natural selection. To do this, the authors drew upon several key aspects of how children (and adults!) learn science. First, understanding the process of natural selection requires significant "content knowledge" of organisms' structures and functions and their interaction with the environment (Gelman and Brenneman 2004). Second, learning experiences need to focus on the "explanatory utility" of ideas (NRC 2007). Finally, throughout the unit they drew on the power of narrative as an aid in building and understanding scientific explanations. The unit described in this article uses the context of crickets to explore the concept of natural selection in ways that capitalize on these three principles. The sequence of lessons described herein is part of a much longer unit on animal behavior and natural selection. However, the section described here has also been taught independently in second- through fourth-grade classrooms in both the United States and China. In all settings, children showed increased understanding of the process of natural selection by unit's end. The authors have correlated these lessons to third-grade "NGSS" goals, but they can be easily adjusted to address either second- or fourth-grade standards as well.