Abstract
Significant effort in the past three decades has been dedicated to the concept of restoring normal neurological functions through stem cell transplants, in devastating neurodegenerative diseases including Parkinson's disease. The aim of this chapter is to present an objective and up-to-date progress in this field. Specifically, the successes as well as the failures and the lessons learned from these outcomes towards further achievements in regenerative therapy are discussed. We build an easily understandable progression from basics to more complex issues and the current challenges in optimizing stem cell therapy in treatment of Parkinson's disease.