U.S. researchers have found a way to turn embryonic stem cells into the cells that make eggs and sperm, which will give insight into a stage of early development that, until now, has been unable to be studied closely.

The planarian is not as well known as other, more widely used subjects of scientific study - model creatures such as the fruit fly, nematode or mouse. But University of Illinois cell and developmental biology professor Phillip Newmark thinks it should be. As it turns out, the tiny, seemingly cross-eyed flatworm is an ideal subject for the study of germ cells, precursors of eggs and sperm in all sexually reproducing species.