In the last 3 decades, stem cells have greatly impacted the scientific and lay communities, providing huge advances in the treatment of devastating human diseases, including myocardial infarction, diabetes, muscular dystrophy, cystic fibrosis, cirrhosis, and osteoporosis. Alongside debates of induced pluripotent stem cells and embryonic stem cells has been the discovery of adult stem cells in many different tissues. While these organ resident or progenitor stem cells offer prospects to contribute to tissue regeneration, they also present challenges because of the complexity of organ...