Scientists have created sperm from the stem cells of rats.
Sperm has been created from the stem cells of rats
The breakthrough gives hope to infertile men - with one in seven couples having trouble conceiving and the problem lying with the man in half the cases.
The lab-grown sperm cells were injected into male rats and were then used to create babies.
The 'tour de force' breakthrough began with stem cells taken from rat embryos and scientists at the University of Tokyo encouraged the cells to transform into super cells by creating a chemical 'soup'.
In the rodent equivalent of IVF, the cells were injected into the testes of rats to become mature sperm before then being injected into eggs.
It led to the successful birth of several baby rats.
Professor Robin Lovell-Bridge, from the Francis Crick Institute in London, said the findings "bode well" for attempts to create human sperm.