Sperm have been made in the laboratory and used to father healthy baby mice in a pioneering move that could lead to infertility treatments.
The Chinese research took a stem cell, converted it into primitive sperm and fertilised an egg to produce healthy pups.
The study, in the Journal Cell Stem Cell, showed they were all healthy and grew up to have offspring of their own.
Experts said it was a step towards human therapies.
It could ultimately help boys whose fertility is damaged by cancer treatment, infections such as mumps or those with defects that leave them unable to produce sperm.
Sperm factory
Making sperm in the testes is one of the longest and most complicated processes in the body - taking more than a month from start to finish in most mammals.
Read more: Lab-grown sperm makes healthy offspring
Source: bbc
