Research has shown that technology-enhanced visualizations can improve inquiry learning in science when they are designed to support knowledge integration. Visualizations play an especially important role in supporting science learning at elementary and middle school levels because they can make unseen and complex processes visible. We identify 4 principles that can help designers and teachers incorporate visualizations into curriculum materials. These principles call for (a) reducing visual complexity to help learners recognize salient information, (b) scaffolding the process of generating explanations, (c) supporting student-initiated modeling of complex science, and (d) using multiple linked representations. We describe the principles, discuss patterns combining the principles, and give examples from several science disciplines. (Contains 9 figures.)