Researchers gave lab mice some very human guts. (Robert F. Bukaty/AP)

In a recent Nature Medicine study, scientists reported using human stem cells to grow working intestines in lab mice. The experiment serves as a stepping-stone towards both lab-grown organs on demand and better animal models of human disease, WIRED reports.

The Cincinnati Children's Hospital researchers first used bioengineering techniques to turn the stem cells into the cellular precursors of intestinal tissue. Once these so-called "organoids" were transplanted into mice (which had been genetically modified to avoid the immune rejection of human cells), they grew into functional intestines.

The organoids were implanted into the kidney capsules of the mice. This is the tough protective layer of the kidney, and it provided a safe space and ample blood supply for the growing organ. After six weeks, the new intestines were larger than the mouse kidneys themselves -- and had replicated almost all of the tissues present in a human intestine, including those needed to digest food.

Researchers are hopeful that this marks progress toward growing on-demand tissues to replace intestines damaged by illnesses such as cancer and Crohn's disease. But it could take years for their work to move from mice to humans.