Stem cells could be the key to treating all kinds of ailments ranging from deseases like Alzheimer's or Parkinson's to physical injuries like spinal traumas. But creating stem cells is a tricky business. In order to perform the necessary experiments to develop treatments, researchers need large batches of identical cells. Often, this means catalyzing growth using materials that include proteins or cells from mice. These materials drive stem-cell growth for lab-bound cells, but if they were actually integrated into a human body there would likely be an immune reaction.