This volume covers the most recent progress and development in the physical mechanisms, materials technology, properties and applications of electrorheological (ER) fluids. It includes papers about a newly emerging material, magneto-rheological (MR) fluids, as well. The science of ER fluids and MR fluids is making a great impact on industry and technology. Contributions come from leading experts in the field. This volume serves as a stimulating and valuable reference for students and research workers in condensed matter physics, materials science, chemistry and engineering. It not only gives details about the leading edge of research and applications, but also provides an overall view of the field.