This unit of the Flexible Learning System (FLS) describes the development of children's concepts and presents ways that adults can facilitate conceptual learning in children between 2 and 8 years of age. Concepts are described as representable, sharable and organized knowledge formulated around interests, susceptible to agreement and disagreement, and in some cases, capable of being forgotten. Suggested activities for adults involve analysis of adult concepts and their representation, adult classification activities, interviews of children, classroom observation, and thought problems. Activities are designed to explore ten characteristics of concepts; how concepts are organized; how the organization of concepts changes with mental development; how concepts are represented; how interests determine the formation of concepts; and guidelines for educational practice that support conceptual growth. Written material provides an introduction and follow-up to each activity. The appendix contains notes on clinical interviewing of children and a bibliography. Familiarity with the content of the series "Exploring Children's Thinking," also a part of the FLS, provides a foundation for understanding this book. An understanding of the mental development of classification skills is considered prerequisite. Other related FLS materials: "The Growing Mind"; "Developing Children's Sense Perception"; "Using Toys and Games with Children"; "Understanding Children's Play Through Observation"; "Problem Solving with Children." (Author/SB)