A team of Japanese scientists have managed to extract a sample of sperm from mice.

It is one of the most complex substances produced in the body, and one that has puzzled researchers for years. It will be able, scientists hope, to provide hope for infertile men.

Sperm has been created before, CNN notes, but until now no man-made sperm had yet to produce results. Or baby mice in this case.

Perhaps fittingly, like making babies; making sperm takes time too. In most mammals it is a process that lasts a month or more.

Scientists told James Gallagher of the BBC that rather than working with individual cells as in previous studies, they studied sperm fragments.

“It’s one step in finding therapeutic help for infertility.  Lots of avenues are being explored,” Dr. Rocky Ward, assistant professor of Biology at WTAMU, said “Maybe this is ultimately the answer, maybe not. We’ll see.”

But the researchers, working at Yokohama City University Graduate School, found out more than the fertility levels of the team’s work, according to their report in Nature.

They also found that the fertile sperm could be frozen and saved for later use.

This could be great news for former cancer patients, whose fertility is often compromised by chemotherapy and radiation. These patients, according to the Telegraph, cannot currently preserve their sperm before the disease robs them of their reproductive abilities.

The samples stayed frozen for months, the report said.

Another group this study may help is women. However, producing fertile eggs for females (both mice and human) is much more difficult.

“I think it is very possible that they will try to replicate their results with female eggs,” junior Wildlife Biology major Samantha Tessneer said. “Although I can imagine it will be much more difficult because of the complex reproductive system in females.”

The study could have an impact on the study of mice as well as the study of humans.

If future tests are successful, the challenge will be making sure that the research remains ethical.

“All research must be ethical. Human research must reach a higher standard.  Research that involves manipulations that can produce changes to genomes is especially worrying,” Ward said. “That doesn’t mean the work shouldn’t be done, but it should be done right, with overview by other biologists and bioethicists.”

Scientists have warned that this is just one study and it will need to be tested and replicated.

Whether or not scientists will be able to create working sperm for humans remains to be seen.

So far, none of the experiments have worked on humans.

“That’s usually a very long time.  Human research must always be carefully considered and painstakingly conducted,” said Ward. ”Investigations into human therapies can take many years.  Manipulations that involve germ lines, such as this work, are especially problematical.”