Stem cells can simply be defined as cells that possess differentiation potential and the ability to self-renew. Since their discovery research in this area has continued to increase. One of the main reasons for this is due to the high potential they have in treating illness and disease. It was initially thought that neurons were unable to be replaced. However, there is now much research indicating that the process of neurogenesis does take place in the brain. This therefore has spurred on much research to see the role that stem cells have to play in treating neurodegenerative diseases, which are characterized by the loss of neuron and glia. If we are able to find a way through the use of stem cells to replace lost neurons and glia we would be well on the way to finding a cure for many neurodegenerative diseases.