This volume contains the selected papers presented at the 10th international workshop sponsored by the Japan Fine Ceramics Center, 'Grain Boundary Engineering in Ceramics: From Grain Boundary Phenomena to Grain Boundary Quantum Structures,' which was held on March 15-17, 2000, in Nagoya, Japan. This workshop, on timely topics of ceramic materials, is held every two years. Since most advanced ceramics are fabricated by sintering raw powders, grain boundaries play a key role in sintering behavior and affect various properties. This meeting discussed grain boundaries in ceramics not only from conventional approaches, but also from novel approaches, including microscopic analysis of local atomic bonding or even quantum structures of grain boundaries. This type of microscopic analysis will enable the design of new ceramic materials in the near future. Recent data has shown that various properties in ceramics can be controlled by the presence of small dopant ions in grain boundaries, which supports this prediction. A number of top-level scientists came from around the world to join this meeting, making the workshop an exciting event with many lively discussions. The high-quality papers compiled in this proceedings are evidence that leading experts attended. It is the hope of the editors, and the Japan Fine Ceramics Center, that this volume will be a guide to designing new ceramic materials in the future.