When it comes to learning about solids, liquids, and gases, children often bring interesting yet inaccurate ideas to the topic. When children’s ideas conflict with the concepts we seek to teach, they interfere with learning. Therefore, we must consider ways to elicit children’s thinking and match instruction and learning experiences to the knowledge, skills, and ideas learners bring with them. Here the authors present strategies for tapping into children’s ideas about matter and using them to inform instructional planning.