A set of core ideas in the life sciences revolve around genetics, variation, and inheritance. While the "Next Generation Science Standards" (NGSS; NGSS Lead States 2013) emphasize teaching and learning about these concepts across K-12 grades, it is critical for early learners to begin to develop understanding of them. By the end of fifth grade, students should understand that "many characteristics of organisms are inherited from their parents" and "different organisms vary in how they look and function because they have different inherited information" (NGSS Lead States 2013, p. 29). This article presents a one-week instructional sequence from a six-week curriculum module to support third-grade students in developing understanding of inheritance and variation in living things by engaging in scientific modeling. Scientific modeling is a science and engineering practice emphasized in the "NGSS" in which students develop and use representations of scientific concepts, processes, or phenomena (Forbes et al. 2015; Kenyon, Hug, and Schwarz 2008). In this unit, students develop and use models to investigate the corn life cycle, structure and function, and inherited traits through hands-on investigation, data modeling, and other learning activities that build upon their existing understanding of the key life science concepts, such as life cycles and reproduction. The "NGSS"-aligned curricular sequence from the unit highlighted here explores three key ideas: (1) how resemblance between parents and offspring is related to the process of inheritance; (2) how inherited traits are passed from parent to offspring via coded instructions; and (3) how a mix of traits for multiple characteristics creates variation in a population of plants.