James Gallagher at the BBC:
Stem cells made from skin have become “grandparents” after generations of life were created in experiments by scientists in Japan.
The cells were used to create eggs, which were fertilised to produce baby mice. These later had their own babies.
If the technique could be adapted for people, it could help infertile couples have children and even allow women to overcome the menopause.
But experts say many scientific and ethical hurdles must be overcome.