This poster describes and presents findings from a multi-year design-based research study. The focus of the work is how to design and implement science investigations that make productive use of the uncertainty that scientists experience as they conduct investigations. Specifically, we have developed a framework that situates empirical activity in a modeling enterprise, and names and situates common forms of uncertainty found in science investigations. We used the framework to co-design, analyze, and re-design investigations in partnership with early elementary (Grade 2) and upper elementary (Grade 5) teachers. The poster presents two central design tools emerging from this work. These support curriculum designers and teachers to implement the uncertainty in science investigations in nuanced ways, making choices based on the specific investigation’s affordances, conceptual goals, and student resources.