Stem cells are the basic building blocks of animals, forming in the new embryo and later developing into the various organs and tissues as the fetus grows.
Researchers have grown stem cells into many other types of cells, including egg cells, but this is the first time a sperm cell has been developed, the scientists said.
The work is very preliminary, and was done in the laboratory with mouse stem cells. The next step would be to see if it can be repeated in live animals.
The work was headed by Toshiaki Noce of Mitsubishi Kagaku Institute of Life Science in Japan. Noce and his team incubated the stem cells with other cells that produce a protein called BMP4, which is known to stimulate formation of sperm cells during the development of an embryo.
In their laboratory, some of the stem cells began developing into sperm cells within one day, a process that takes three days in the embryo.
Growing stem cells into other tissues has been hailed as a source of major potential therapies in the future.
However, the process is controversial because many stem cells are harvested from discarded embryos.