Stem cells are special human cells that are able to develop into many different cell types. This can range from muscle cells to brain cells. In some cases, they can also fix damaged tissues. Researchers believe that stem cell-based therapies may one day be used to treat serious illnesses such as paralysis and Alzheimer disease.A number of stem cell types including oligodendrocyte progenitor cells (OPCs), motor neuron progenitor (MNP) cells, neural stem cells (NSCs), mesenchymal stem Unipotent stem cells give rise to cells of their own type along a single lineage. As such, unipotent stem cells have the lowest differentiation potential. In stem cell transplants, stem cells replace cells damaged by chemotherapy or disease or serve as a way for the donor's immune system to fight some types of cancer and blood-related diseases, such as leukemia, lymphoma, neuroblastoma and multiple myeloma. These transplants use adult stem cells or umbilical cord blood. Stem cells, either carrying the disease gene or engineered to contain disease genes, offer a viable alternative. Stem cells from the umbilical cord are special.