'Cloning' makes human stem cell
5 October 2011 Last updated at 18:26 BST
A form of cloning has been used to create personalised embryonic stem cells in humans, say researchers.
Genetic material was taken from an adult skin cell and transferred into a human egg. This was grown to produce an early embryo.
Stem cells have huge potential in medicine as they can transform into any other cell type in the body.
However, the stem cells formed contained chromosomes from both the adult and the egg cells.
Lead researcher at the New York Stem Cell Foundation Laboratory, Dieter Egli, explains his hopes for the future using this technique.