Increasingly, research on cognition, learning, and education seeks to understand the cognitive processes underlying conceptual understanding. This is especially true for efforts to understand how students learn science. The present case summarizes work that examines 6- to 10-year-old students engage in scientific reasoning to learn new scientific knowledge. In the reported work, students participate in guided experimentation to learn about thermodynamics concepts. Data are analyzed to assess whether children can learn about complex scientific phenomena via experimentation activities. Data collection includes interviews, paper-and-pencil worksheets, and lab notebook artifacts. This work illustrates diverse methodologies for supporting research on science learning and measuring student understanding.