South Korean scientists have cloned 30 human embryos to obtain cells they hope could one day be used to treat disease.
Some believe the technology is a great breakthrough, but others have profound moral concerns.
BBC News Online canvasses opinion.
Linda Kelly is chief executive of the Parkinson's Disease Society.
It's a very significant first step forward, but I would stress it is a first step. What it does is give the potential for a sustainable source of material.
Linda Kelly said much more work is needed
But is some way before we have a change of treatment. It could be many years yet.
In Parkinson's the cells in the brain involved in movement die, and the idea behind stem cells is that they might be able to replace those cells.
But just because you have a source of them doesn't mean you have the techniques to put them into the brain, or that then they can actually last in the brain and produce the chemicals that are involved in movement.
In the UK we have very strict, open and transparent legislation, and I think that is so important. If you had Parkinson's and you were going to have stem cells put into the brain you would want to know the source of them, and the risks, as well as the benefits to you.
There are many areas to explore. Stem cells are important, but they are not the only thing. It is important we continue to research all the avenues because ultimately Parkinson's is probably not going to be one condition, but a number of different conditions, so we need a range of methodologies and possible treatments.
Dr Patrick Dixon, author of The Genetic Revolution.
It's an important announcement, but we need to see it in context. It is actually very difficult to grow embryonic stem cells, and they can go out of control quite easily and can become cancers after being put inside people. So we need to be very careful before saying this is a spectacular breakthrough.
And the other thing we need to understand is that cloning human beings to produce
embryos, and then taking those embryos to bits to take tissue from them is actually looking like a last century science.
Dr Dixon says less controversial technology could be used
Most scientists who are interested in stem cell research have moved away from embryonic stem cells, and are using adult stem cells.
We are seeing astonishing progress using an alternative to embryos which is not controversial, has no ethical problems and may well deliver many of the same benefits if given enough funding.
If I take a cell from your body and fuse it with one of your own eggs and make an identical cloned embryo of you it could be taken to bits for medical research, or it could be put inside a mother to produce your cloned twin.
And the fact of the matter is that there are all kinds of people who are intent on doing the second. They want to use the results of the first for the second, and inevitably they will succeed.
Patrick Cusworth, from the anti-abortion charity Life.
The fact that this is the first group to provide evidence of their success in cloning human embryos is nothing to be proud of. The potential for this kind of experiment is horrific.
In creating 30 tiny new human beings - at the expense of 212 other attempts - these scientists have demonstrated contempt for early human life.
Dr Hwang has claimed that, since it is his intention to use these embryos for destructive research alone and that he is opposed to full pregnancy cloning, his experiments are morally acceptable. They are not.
To create a new human being with the intention of mutilating and destroying it can never be justified in a civilised society.
Alas, that is now permitted in our country. Our government insists that full pregnancy cloning will never be allowed, but we may be sceptical about that promise.
The only way forward is to ban all forms of cloning.
Suzi Leather, chair, UK Human Fertilisation and Embryology
It is a very exciting advance and it has come from a reputable group in South Korea. I think we can have confidence in their science.
These aren't cowboy cloners. And I think we can have confidence also in their ethical approach.
This is therapeutic cloning, which is very different from reproductive cloning.
The scientists are trying to develop new therapies for degenerative diseases, such as Parkinson's, such as diabetes, which would involve tissue transplants of cells matched with the patients needing them so that there is not a risk of rejection.
Such work would be permissible in the UK. We haven't had any applications so
far, but I would very much welcome an application because I think the potential
benefits are very great.
We should be clear that the benefits to patients are a very long way away. This is a hugely important first step.
Dr Ian Gibson, chairman of the House of Commons science and technology select
It's a step forward in terms of producing stem cells. That is bound to be good news for patients with Alzheimer's, Parkinson's and various other muscular disorders.
It is a complete vindication of the Government's position in allowing stem cell research in this country.
Even people like Christopher Reeve - Superman himself - have acknowledged it is a real plus.
There is no justification for producing human embryos (for reproductive cloning) and every justification for producing stem cells for transplantation purposes.