The goal of this four-year project is to develop video case studies on scientific sense-making, these materials can then serve as catalysts and models for moving teachers in middle grades (4-8) toward a sense-making perspective in science and for linking that perspective to new teaching and assessment practices. The project will integrate research based on intensive work with teachers from diverse backgrounds, video case study development, inservice delivery, and evaluation. The aim is to first build, through collaborative research involving teachers, science educators, scientists, and educational researchers, a knowledge base an critical sense-making practices for teacher development in science. The project will then use what has been learned to create a corpus of ten video case studies in scientific sense-making and an accompanying handbook for use in a range of inservice contexts. The project final phase will be a documentation of the effectiveness of the video case studies in promoting a sense-making perspective among teachers in field tests during three contexts: single session workshops, and long term sustained development. The cost sharing will be 11% of the NSF portion.