Sperm have been made in the laboratory and used to father healthy baby mice in a pioneering move that could lead to infertility treatments, reports BBC.

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 men whose fertility is damaged by cancer treatment, infections such as mumps or those with defects that leave them unable to produce sperm.

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. Now scientists have been able to reproduce the feat in the lab.

An embryonic stem cell, which can morph into any other type of tissue, was guided towards becoming sperm with a cocktail of chemicals, hormones and testicular tissue. In order to develop properly the cell must go through a crucial and delicate rearrangement of its DNA — its code of life — called meiosis.

But they did not create sperm as you would recognise them with a head and a tail for swimming — they were a stage earlier known as spermatids.

However, the spermatids have the correct amount of genetic information and were successfully inserted into mouse eggs through IVF.