The study of microglial cells has recently gained importance for those researching degeneration and regeneration. Microglia in the regenerating and degenerating CNS supports the assertion that understanding microglial biology could perhaps be pivotal for unraveling the pathogenetic mechanisms that underlie Alzheimer's disease, In addition, microglia are also critical for understanding the sequelae of traumatic brain and spinal cord injury, and for the important post-traumatic repair processes. This book gives an up to date account of the role of microglia in degeneration and regeneration of the nervous system and reviews their cell function and physiology.