Research into the causes of neurodegenerative diseases like Parkinson's- and Alzheimer's disease has long been hampered by the lack of access to live disease-afflicted neurons for in vitro studies. The introduction of induced pluripotent stem (iPS) cells has made such studies possible. iPS cells can be reprogrammed from somatic patient-derived cells (e.g. skin cells) and differentiated into any cell type of the body. This allows for the production of neurons, which have the genetic background of the patients and show disease-relevant phenotypes.