The scientists, who come from the University of Tokyo and Kyoto University, say the ear could be grown to repair faces disfigured in battle or accidents and also help people born without ears or with ear deformities. The researchers at the two state-run universities cultured human induced pluripotent stem cells into cartilage cells, which were then made into numerous tiny balls. In about two months, the tubes dissolved, leaving behind on the animal’s back what looks like a 5-centimeter human ear. 8 Animals That Can Regrow Their Body Parts 
 
 It’s not the first time researchers have grown an ear on the back of a rat. The researchers hope they can use the new technology in treating patients born without ears or with small ears, with a clinical study involving humans expected to start in five years.
– Cool—and/or creepy—news out of Japan, where researchers at the University of Tokyo and Kyoto University have created a human ear ... on the back of a rat. The researchers used stem cells that grew into ear cartilage, shaping the cells into an ear by putting them in "biological tubing," Discovery News reports. More specifically, they used "induced pluripotent stem cells," which the National Institutes of Health explains are "adult cells that have been genetically reprogrammed to an embryonic stem cell-like state." The ear-shaped cartilage was implanted under a rat's skin, where it was allowed to grow for two months; the tubing dissolved and a 2-inch-long ear was left behind. The researchers believe this technology could be used to treat people who are born with no ears or with smaller-than-normal ears, Japan Today reports. It could also be used to repair ears disfigured in accidents, Discovery adds. In the case of a child born with a missing or misshapen ear, the researchers note that the ear they created is "living," and thus would develop and grow along with the child. A clinical trial involving humans is expected to start in five years. In 2013, researchers in Boston used sheep cells, bovine collagen, and an ear-shaped titanium wire frame to grow an ear on the back of another rat, Discovery notes. (These creatures can grow the heads and brains of other species.)