Stem cells have the ability to self-renew and differentiate into various cell types, replacing dead or damaged cells throughout life. There are various sources of stem cells including embryonic, adult, fetal, and umbilical cord blood stem cells. Stem cell therapy works by transplanting stem cells to treat conditions such as blood disorders, baldness, burns, diabetes, blindness, Parkinson's disease, brain damage, tooth loss, kidney damage, deafness, orthopedic issues, and heart damage.