When it comes to growing intestines, the first inch is the hardest—especially in a petri dish. Scientists at Cincinnati Children's Hospital Medical Center have met that benchmark: they recently reported in Nature Medicine that they had grown a piece of gut—nerves, muscles and all—from a single line of human stem cells. In the future such tissue could be used for studying disease and more.

In 2011 researchers at the same center announced that they had grown intestinal tissue—but it was missing nerve cells and so was unable to contract in the undulating motion that pushes food along a colon. This time around, the scientists grew neurons separately and then combined them with another batch of stem cells that had been induced to become muscle and intestinal lining. Voilà: an inch-long piece of gut formed. “Just like in developing human bodies, the nerve cells knew where to go,” says Michael Helmrath, surgical director of the Intestinal Rehabilitation Program at Cincinnati Children's.

The scientists then transplanted the tissue onto a living mouse's intestine so it could mature. After harvesting it for testing, they stimulated the bespoke chunk with a shock of electricity. It contracted and continued to do so on its own. “The function was quite remarkable,” Helmrath says. Intestines now join kidneys, brain matter and a few other kinds of tissue that can be grown in the lab.

Next, Helmrath and his colleague Jim Wells would like to coax longer pieces of intestine by working with pigs. Eventually the researchers hope to help treat people with gastrointestinal problems by making copies of a patient's gut to observe how a disease manifests—or even to transplant the tissue. “Intestines are a complex structure to grow,” Wells says. “That we've even gotten this far in such a short time gives me hope that we can grow something therapeutically useful in the long run.”