Stem cells are growing cells in a laboratory dish that have the potential to become any kind of cell at all. This is based on fusing a human somatic cell with a bovine egg cells from which nucleus has been removed, may enable the production of an unlimited supply of stem cells for transplant medicine. Researchers say that this technique may remove two barriers in current transplantation therapies. First it may overcome the problem of tissue rejection because cells generated by nuclear transfer are genetically identical to the patient. Second, the technique may provide an accessible source of cells to help meet the current demand for large quantities for transplantable tissues.Embryonic stem cells provide an unlimited supply of cells that may be grown in the laboratory into virtually any type of tissue for transplant use. "Thousands of people die every year waiting for an organ that their body won't reject and they never find it. Locked in every cell is the body, is the information to make a whole body," said Dr. Michael West, Advanced Cell Technology's chief executive. A few cells from a patient can be taken and grow them perhaps into heart cells, for use in repairing a damaged heart or brain cells for injection into damaged brains of Parkinson's patients. If you had a large population of uniform heart cells, you could use them for drug testing. Most stem cells have a function. They are liver cells, skin cells, brain cells, and so on-- once they have taken on this function, a process known as differentiation, there is no going back. They got five different independent cell lines to grow. A cell line is a laboratory dish of cells that are living and dividing as if they were in the body. "What we can do now is grow a number of different cells, including muscle, cartilage and neurons" said James Thompson, a developmental biologist at the University of Wisconsin at Madison. Thompson thinks huge banks of frozen cells could be established, each tissue type in the same way that organ donors now are. Such technology might be possible in five years.