Exploratory learning is recognized as a developmentally appropriate practice in early childhood education. During exploration, exposure to new things guides children in the acquisition of knowledge, while interactions with a range of familiar and unfamiliar artifacts can support developmental integration. Exploratory activity may occur spontaneously at any time, but it can also be structured and guided to achieve specific curricular and developmental goals. This paper explores preschool children's interactions during semi-structured exploratory activities in three different conditions. Thirty-five 4- to 5-year-old children, from six preschool classrooms, were randomly assigned to three different conditions. Each condition included the same set of 13 different artifacts that were either artistically rendered in black ink on white paper ("sketch condition"), included in a children's story book ("book condition"), or had the real artifact itself ("tangible object condition"). Children's exploration and interactions were videotaped and analyzed to see which, if any, of the three conditions would appear to stimulate and encourage early "engineering thinking" the most. Initial hypothesis was that the "tangible object" condition would appear to be the most beneficial. Findings showed that this condition elicited the longest discussions and interactions with the artifacts, and it was also the condition during which children were demonstrating more knowledge and ideas with regard to possible functions of the artifacts. Regarding whether there was a condition that stimulated more interest toward specific artifacts, no clear pattern among the three conditions appeared. Implications are discussed in terms of preschool Science, Technology, Engineering, and Mathematics (STEM) and child development. (Contains 4 tables and 3 figures.)