Look, no embryos! The future of ethical stem cells

It is unclear at exactly what point the phrase "stem cell" entered the vernacular, one of very few scientific terms that achieve the status of, say, DNA in not requiring a detailed explanation every time it is written down or spoken.

Whether or not you know exactly what they are or what they do, stem cells imply something very specific: in them is invested the next generation of medicine, revolutionary treatments for everything from Parkinson's to Alzheimer's. On the horizon, there is also the hope of growing genetically matched tissue (even whole organs) to replace anything that has been damaged by disease or accident.

But perhaps the reason stem cells managed to lodge themselves so deep in the public psyche was not just because of their awesome scientific potential, or their ability to turn into the treatments of the future. Perhaps it was politics. For years, stem cells dominated all other science stories in newspaper headlines because they framed an ethical conundrum – to get to the most versatile stem cells meant destroying human embryos.

Research on stem cells became...