Teaching students learn to think like scientists is one of the purposes of science education and the premise of this study is to understand the processes of scientists' visualization. In order to understand the involved aspects while scientists visualizing the complex concepts, this study interviewed one scientist and explored his thinking processes while he constructed visualizations of the concept of carbon cycling in the ecosystem. The interview consisted of visualization tasks with think-Aloud and the follow-up retrospective. By the analysis of the information of interview of a scientist, this study found that cognitive skills, metacognitive skills, visualization skills, conceptual knowledge, metacognitive knowledge, and meta-level visualization knowledge were interactively used by a scientist. We identified six strategies demonstrated by the scientist constructing visualizations. Moreover, two critical points influenced the visualization task were identified. By the cross-case comparison and revealing the gap between scientists and novices in the future, this study spurs discussion to propose concrete scaffolding in instruction and curriculum design for students.