Researchers in Japan have made fertile mammalian sperm in a culture dish, a feat long thought to be impossible. The technique, reported today in Nature1, could help to reveal the molecular steps involved in sperm formation and might even lead to treatments for male infertility.

Biologists have been trying to make sperm outside the body for almost a century. Failure has often struck at the stage of meiosis, a type of cell division during which paired chromosomes swap DNA and the number of chromosomes per cell is halved. The result of this process is sperm cells ready to fuse with an egg.

via Sperm grown in a test tube : Nature News.