Scientists have found another source of stem cells for research - the pulp of a child's first set of teeth.
Child teeth could be a source of stem cells
The finding, by dental researchers in the US, could further fuel the debate over the need for such cells to be taken from human embryos.
Stem cells are the body's "master cells" - they have the potential to develop into a wide variety of different types of cells.
Many scientists hope that they will one day be able to use stem cells to replace vital tissues lost through disease or injury.
Currently, the undeveloped embryo offers stem cells in their purest form.
The stem cells in the tooth are likely latent remnants of an early developmental process
Dr Songtao Shi, National Institute of Dental and Craniofacial Research
However, there is fierce ethical opposition to these experiments, and many scientists are looking for an alternative source.
The latest research, published in the Proceedings of the National Academy of Sciences, involves cells extracted from the pulp of deciduous, or "baby" teeth, which normally fall out around the age of six or seven.
Dr Songtao Shi, from the National Institute of Dental and Craniofacial Research, said that the cells they found had the ability to be manipulated in the laboratory to form bone, dentine (tooth) and even nerve cells.
It is the latter that is likely to be of most interest to researchers, as the hope is that neuronal stem cells will one day be able to help treat nerve damage.
The teeth in question were retrieved from Dr Shi's daughter Julia.
He said: "Once it was out, we sat and looked carefully at the tooth."
Seeing some red-coloured tissue, he extracted it and went to examine it in the laboratory, and managed to extract living stem cells from it.
Further experiments on baby teeth retrieved from other children as nature took its course, revealed more cells which had the ability to grow in laboratory culture.
He said: "Doctors have successfully harvested stem cells from umbilical cord blood for years.
"Our finding is similar in some ways, in that the stem cells in the tooth are likely latent remnants of an early developmental process."
Professor Peter Andrews, a stem cell researcher from the University of Sheffield, said the finding was "plausible", probably the result of the same process which allowed certain stem cells to be extracted from bone marrow.
He said that the embryo remained the most practical current source of stem cells.
He said: "They are the best defined and characterised - and we know how they can be turned into lots of different things.
"They remain the cells about which we know the most."