This article provides background and tips for using the “Needs of Seeds” formative assessment probe. Students demonstrate pre-knowledge as to whether or not seeds have needs both similar to and different from mature plants and other living organisms. The probe reveals whether students overgeneralize the needs of seeds by assuming they have the same needs as the adult plants that grow and develop from a seed during the life cycle of the plant. “Needs of Seeds” provides an assessment springboard for students to learn about the needs of living things, hone their skills of inquiry, and experience the nature of science. In addition, teachers can gather valuable formative assessment information about their students’ thinking and their ability to identify the evidence they need to support their ideas.