Stem cell science has been hailed as modern medicine's best hope - to treat the untreatable, to keep us fit in old age and even, perhaps, to help the severely disabled to walk again.
But scandal in South Korea has rocked this science - with one of its leading proponents labelled a fraud, and as the scientists reflect on the ethics of their work and its practical limits, where does this leave us, the potential patients?
Stem cells, unlike ordinary cells, have the unique power to re-create themselves when they divide.
There are two types: the first, adult stem cells, are cued up to become particular cell types - say nerve, blood, bone or heart. These can carry out valuable repairs - but only in their specialist part of the body.
The second group is embryonic stem cells. Found in the early human embryo, these are highly sought after because they can re-create themselves indefinitely. Also, since they are not yet switched to become specific cell types, they have the potential to repair damaged and diseased organs anywhere in the body.
Human egg use
We spoke to experts in both stem cell types, to gauge the impact of the scandal of Dr Hwang - the stem cell scientist in South Korea who seemed so far ahead.
Dr Hwang claimed to have created 11 stem cell lines from human embryos, cloned so that the cells exactly matched an individual patient - the Holy Grail of stem cell science.
Is there still the enthusiasm for stem cell science in the wake of the Hwang scandal?
It turned out much of his work was fake, and crucially that he'd had to use far more human eggs than he'd said.
The challenge now, for embryonic stem cell scientists at least, is to find ways to make stem cells without using vast quantities of human eggs - in short supply and, for some, ethically questionable.
Stephen Minger, from Kings College in London, created the UK's first embryonic stem cell line, in 2003.
Until now, he's relied on creating stem cells from left over embryos from IVF.
Before the Hwang expose, he had hoped to join the elite club of scientists using cloning to study the cellular processes behind disease.
Now, to avoid using up human eggs on an uncertain technique, he has a plan for a new - and potentially controversial - way around that: cloned human-animal hybrids.
"What we and others would like to do is use non-human eggs - for instance rabbit eggs," Dr Minger says. But therapies, he adds, are at least 10 years away.
A team at the University of Cambridge has another plan. Roger Pedersen, director of the centre for stem cell research at the university, told us about a plan that avoids cloning, and fresh human eggs, and relies instead on off-the-shelf matches from a bank of stem cell lines from selected donors.
Then there's the man with a third way to avoid the need for human eggs. Mohammed Taranissi runs one of the UK's most successful fertility clinics.
He's promoting what he calls "stem-brid" technology, which uses the stem cell line itself as a surrogate egg.
But there's a new realism now among embryonic stem cell scientists about how long it will be before they can help people.
Adult stem cells
That leaves their counterparts working on adult stem cells. They now expect to deliver treatments much sooner.
One team, at the London Chest Hospital, is using adult stem cells taken from a patient's own bone marrow to try to repair the damage caused by a heart attack.
Dr Anthony Mathur is the cardiologist in charge of the trial - the largest of its kind in the world.
He told Newsnight: "My passionate feeling here is that this type of therapy, cellular therapy, is going to revolutionise the way we practice medicine."
Half the patients are treated with stem cells and half with just the fluid, or growth factor in which the cells are found.
Neither Dr Mathur nor the patients know who's getting what but that's crucial in order to gather definitive, scientifically controlled data.
Clinical trials 'within this year'
Across London, another adult stem cell trial could yield results within months. At the Institute of Neurology, they hope to use unique adult stem cells from the lining of a patient's own nose to treat nerve and spinal cord injury.
Professor Geoffrey Raisman, who's leading this research, told Newsnight:
"The interest in embryonic stem cells has led to adult stem cells being very much neglected. And whereas I think for embryonic stem cells we're talking about a long time ahead before these cells are going to be in use, in our case we're thinking of clinical trials within this year."
It would seem a safe bet that adult stem cells will deliver first - but the enthusiasm for this science as a whole is still there, despite the reality check brought about by Dr Hwang.
Susan Watts' report was shown on Newsnight on Thursday, 9 February, 2006.