Reported is a teacher-developed project in individualized instruction in elementary science made up of a re-organization of existing curriculum materials with a four theme framework - Energy, Matter, Life and the Universe. This program is based on the assumption that freedom and activity will lead to new understanding in science through discovery and other processes. The program was developed around the three existing curriculum materials: "Concepts in Science" by Brandwein, "Science, a Modern Approach" by Fischler, and "Science for Tomorrow's World" by Barnard. During the first year, 450 students from grades two and three (Division 1) and four, five and six (Division 2) were involved. During the second year, 500 students were included. The rationale, organization, operation, and an evaluation of the program is presented. The Thematic Elementary Science Individualized Studies (THESIS) program requires student freedom, student selection and student opportunity to change his selection. The program could not accommodate students in grade one due to their lack of school experience and inability to read. Students in grades two and three needed more maturity and students in grades four, five, and six all required intital teacher-grouping assistance. None of the second and third graders and only a small number of the others appeared to possess the self-direction required. (EB)