Human eggs have been grown in the laboratory for the first time, say researchers at the University of Edinburgh.
The team say the technique could lead to new ways of preserving the fertility of children having cancer treatment.
It is also an opportunity to explore how human eggs develop, much of which remains a mystery to science.
Experts said it was an exciting breakthrough, but more work was needed before it could be used clinically.
Women are born with immature eggs in their ovaries that can develop fully only after puberty.
It has taken decades of work, but scientists can now grow eggs to maturity outside of the ovary.
It requires carefully controlling laboratory conditions including oxygen levels, hormones, proteins that simulate growth and the medium in which the eggs are cultured.
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