Research into human cell-growth could open the way for unlimited supplies of material for replacing faulty cells.

The process could revolutionize treatment of conditions such as diabetes and Parkinson's Disease.

Two teams of scientists in the United States say they have succeeded in taking special cells called stem cells from humans and replicating them in the laboratory.

Stem cells can develop into any kind of body cell, including bone, skin or nerve tissue.

However, a BBC science correspondent says such treatment is at least five years away -- and raises ethical questions over the use of genetic material.