Dr Keisuke Kaji, a stem cell researcher at the Medical Research Council Centre for Regenerative Medicine in Edinburgh said the technique was a "great advance" in cell reprogramming technology.

BBC: 'Ethical' stem cell crop boosted

The literature on similarities and differences between ES cells and iPS cells, he said, is quite controversial and scientists still do not know whether differences between different iPS cell lines are just due to genetic differences between the adult cell lines that were used for reprogramming or whether genetic changes occurred during reprogramming.

FORBES: Scientists Relieved As Supreme Court Passes Over Case Against Embryonic Stem Cell Research

It takes about four weeks for a skin cell to be "primed" for reprogramming, and then it takes an additional three to four weeks for iPS colonies to grow, according to Dr. Joseph Wu, study co-author and assistant professor of cardiology and radiology at Stanford's School of Medicine.

CNN: Study: Human fat yields multipurpose stem cells