Scientists have generated for the first time stem cells from adults using the skin cells of two adult men, a new study announced.

The breakthrough, published online in the journal Cell Stem Cell, describes this "therapeutic cloning" of a 35-year-old man and 75-year-old man. Technically called somatic-cell nuclear transfer, the process involves taking the DNA from a donor and inserting it into an egg that has been stripped of its DNA. The resulting hybrid, by encouragement, creates a line of stem cells meant to develop into any kind of human cell or tissue.

The international team used 77 eggs from four different donors, and out of the 39 resulting embryos, the scientists created only one stem cell per donor. Despite the 5 percent efficiency, head chief Dr. Robert Lanza believes in his work.

"This procedure works well, and works with adult cells," he told TIME magazine.

His conviction does not seem so far-fetched given the intricacy of stem cell creation. The Oregon team said a major aspect of their success was allowing the engineered eggs to sit for 30 minutes before hitting them with the charge of electricity that essentially made the egg come alive. The pluripotent stem cells are located on the inside of the thriving embryo.

Lanza and colleagues attribute their success to their breakthrough nuclear transfer technique and to the quality of their donor egg.

"We have another way to skin the cat," Lanza quipped.

But nuclear transfer is a slippery slope in the genetic world. It is the first step in reproductive cloning, a controversial topic since the 1997 announcement that it was used to create Dolly, the clone of an ewe. Since 2005, when the United Nations urged countries to ban the practice, the United States has prohibited the use of federal funds for either reproductive or therapeutic cloning, according to Reuters.