Young children do science exploration and observation every day in their play. They spontaneously engage in parts of the scientific inquiry process--wondering, asking a question, planning how to answer the question, documenting their work, thinking about what happened, and sharing their results with others. Conducting an entire experiment is developmentally beyond most preschoolers, but early childhood educators can teach children to use science process skills by asking open-ended questions, such as, "What do you think will happen if...?" This type of preschool science is most successful when all of the materials may be touched. This naturally lends itself to explorations in which children manipulate materials. In this article, the author shares her experience on how an exploration of chemistry can be a successful addition to a preschool curriculum in a four-year-old preschool class where the author teaches science one hour every two weeks in teamwork with the classroom teachers. The exploration activities introduced by the author in this article pertain to mixing and making changes. (Contains 3 resources and 4 online resources.)