This book explores the potentiel of stem cells for ameliorating the quality of life of patients with neurological and neurodegenerative diseases. It discusses results of pre-clinical investigations and case studies on the effects of stem cell transplantation on cell death, to promote/stimulate neuroprotection after brain and spinal cord injury through trophic support, cell replacement and remyelination. It covers the maintenance of the balance between stem cells and their progenitors within their niche, both under normal and degenerative processes, ischemic stroke, multiple sclerosis, and brain tumor.