This is the second sourcebook that has been produced by members of the Council of Elementary Science International (CESI) in cooperation with the ERIC Clearinghouse for Science, Mathematics, and Environmental Education. This sourcebook is focused on activities designed to enhance children's thinking. Activities emphasizing creativity, inventiveness, visual thinking, and problem solving have been made available to teachers so the activities can be easily incorporated into the teacher's lesson plans. Each activity includes the title, focus (a short description of the concepts and/or skills developed by the activity), challenge or problem posed to students, background information (if needed), a list of materials, suggestions for implementation, further challenges, and references. (Author/PB)