Fifty-six third-year kindergarten student teachers (KTS) were presented with an experimental setting for investigating shadow phenomena. Prior to performing any specific experiment, KTS were asked to externalize their ideas about shadow phenomena corresponding to different configurations of the experimental setting through the use of drawings accompanied by textual explanations. Then, they were asked to perform each of the corresponding experiments and compare the experimental outcomes with their own initial conceptions. The findings clearly demonstrated that the use of drawings and textual explanations triggered students' thinking as they progressively restructured their internal representations. Implications for using visuals in science education are also discussed.