The research was done using fibroblast skin cells
The ability to create stem cell treatments without using embryos is a step closer, say researchers.
A UK and Canadian team have manipulated human skin cells to act like embryonic stem cells without using viruses - making them safer for use in humans.
The cells are reprogrammed by the insertion of four genes which are then removed once the process is complete, they report in Nature.
While a significant step it is early days, the Edinburgh-based experts say.
Much of the work on stem cells has focused on those taken from embryos as they have an unlimited capacity to become any of the 220 types of cell in the human body - a so-called pluripotent state.
But campaigners have objected to their use on the grounds that it is unethical to destroy embryos in the name of science.
In 2007, teams in Japan and the US managed to genetically modify skin cells to be pluripotent, opening the way for a new source of stem cells for use in research.
However, the technique used viruses to genetically modify the cells, which means there was a risk they could become cancerous and so would not be safe for medical use.
The latest study reports a way of delivering foreign genes to reprogramme the cells without using viruses in mouse and human cells.
Furthermore, the team was able to remove the genes afterwards.
Study leader Dr Keisuke Kaji, from the Medical Research Council Centre for Regenerative Medicine at the University of Edinburgh, said nobody, including himself, had thought it was really possible.
"It is a step towards the practical use of reprogrammed cells in medicine, perhaps even eliminating the need for human embryos as a source of stem cells," he said.
But he added they needed to improve the efficiency of the process.
Co-author Professor Andras Nagy, from the University of Toronto, added: "We hope that these stem cells will form the basis for treatment for many diseases and conditions that are currently considered incurable."
Professor Sir Ian Wilmut, director of Edinburgh centre where the research was done and the creator of Dolly the sheep, said it would still take time before these cells could be given to patients.
"Crucially, we need to have a method to generate the desired cell types from these stem cells.
"But I believe the team has made great progress and combining this work with that of other scientists working on stem cell differentiation, there is hope that the promise of regenerative medicine could soon be met."
Professor Robin Lovell-Badge, head of the MRC National Institute for Medical Research, said the research was an exciting step in the right direction but there was still a long road ahead.
"For the time being I think it rather premature to suggest that their work will completely remove the need to derive human stem cells from embryos."
He added there was still a lot to learn from human embryonic stem cells in order to know whether stem cells reprogrammed from adult cells are truly useful or not.
Josephine Quintavalle, of Comment on Reproductive Ethics, said: "This is ethical stem cell research at its best, with embryonic-type stem cells derived successfully from adult tissue without involving human embryos."