Human embryos from skin cells have been created by New York Stem Cell Foundation Laboratory researchers, report sources. These experiments bring cloning closer to reality.
In experiments that mirror the cloning technique used to make Dolly the sheep, they took cells from men's arms and legs and placed them into women's eggs.
The embryos created lived for only five or six days, but they represent a key step in the quest for treatments for incurable diseases from Alzheimer's to cancer.
They placed the DNA from the skin cells inside the eggs and triggered them to grow and divide.
The embryos, and the cells they contained, were mutants with three sets of DNA instead of the two we normally have - one from our mother and one from our father.
But the researchers are confident they will eventually be able to create healthy cloned embryos with the required two sets of genetic material.
The aim of the experiments is not to create cloned babies, but to extract stem cells - 'master cells' capable of becoming any type of body tissue - from the embryos.
"Cell replacement therapy would dramatically change the treatment of, and potentially even cure, debilitating diseases and injuries that affect millions of people," said Susan Solomon, chief executive officer of the not-for-profit organisation behind the research.