Stem cells are young cells that have yet to be developed into a specific cell type and are used by the body to renew tissue and repair damage. In adult stem cells, there are only so many types the cell can develop into. Embryonic stem cells are those present in a developing person when they are still in its mother's womb. Embryonic stem cells have the ability to become any cell in the body, which have a much better applications for medical use.

The researchers have reprogrammed an adult human egg cell to an embryonic state using cloning technology. The cells are self-reproducing lines of embryonic stem cells from the developing embryo.

Though the research is not the answer to the setbacks stem cells have been facing for the past few years, it is a big step forward in stem cell research. The "cloned" cells were close genetic copies of the donor's cells, but for stem cell research to be used in medicine the DNA has to match exactly.

The New York scientists had to start almost from the beginning to develop the new technique. Dieter Egli, the head researcher, removed the chromosomes from an unfertilized egg, and injected two sets of chromosomes from the patient donor's adult cells. The new DNA should drive the cells along their development, but usually growth would stop after a few divisions.

The team found that removing the embryo's DNA was the problem, so they left the original set of chromosomes in. The cells developed fine, but then contained an extra set of chromosomes; three instead of the two normally present. If the technique is to be used for medical purposes, researchers will have to figure out how to eliminate the extra chromosomes.

Stem cell research has a number of applications in the medical field. Stem cells can help with heart diseases, diabetes and cancer. It can also help cure aliments like Parkinson's Disease and Alzheimer's. The cloning techniques can also be used to grow organs for patients with a failing liver or kidney. The cloned organs will be much less likely to be rejected than those donated from other individuals, since the new organs will be genetically identical to the one being replaced.

Stem cell research has been marred by controversy ever since its inception. Originally embryonic stem cells could only be harvested from aborted human embryos. Abortion has been a hot button issue in politics in the pro-life/pro-choice debate.

In 2001, President Bush put sever restrictions on federal funding for embryonic stem cell research. Scientist couldn't harvest any new embryonic stem cells if they wanted to receive funding. In 2009, President Obama eased restrictions, but federal funding for stem cell research is still limited. Scientists now have to rely mostly on private funding for their research.

This marks the first breakthrough in years since a South Korean scientist claimed in 2004 to have created the first embryonic clone from a stem-cell line. But the claim was then shown to be fraudulent.