For many educators, gathering, organizing, and maintaining materials involved in inquiry-based science and math activities can seem daunting. This handbook is designed to help teachers in the task of gathering and maintaining materials to make kits for 42 activities derived from the Great Explorations in Math and Science (GEMS) Program at the Lawrence Hall of Science at the University of California-Berkeley. This book is intended to assist those who already present GEMS units and to encourage more teachers and districts to do so. Sections include: (1) Introduction to GEMS Kits; (2) The Complete Illustrated Kit Inventories, which contains complete materials lists for all 42 current GEMS guides with materials organized as nonconsumable supplies, consumable supplies, and general classroom supplies; (3) The ABC's of Making and Maintaining GEMS Kits, which gives important insights into the basics of making and maintaining GEMS kits, including creative ways to finance kits; (4) Sources of Materials, which lists individual kit items, suppliers, and general supplies; and (5) Interviews with Kit Builders, which introduces eight experienced kit builders who provide concrete suggestions, creative approaches, and valuable lessons learned. (PVD)