Groundbreaking but slightly creepy news has emerged from Japan, where researchers have used stem cells to grow an adult-size, human ear on the back of a rat. Yes, a rat.

The scientists, from the university of Tokyo and Kyoto University, induced pluripotent stem cells to grow into ear cartilage, then placed the cells into a type of “biological tubing” that resembled a human ear, Discovery News reports. It took about two months for the tubes to dissolve, but they did — leaving behind a 5-centimeter human ear. The researchers even took the ear out of the rat afterwards to assess its durability.

“We’ve demonstrated the first full-sized adult human ear on the rat model,” Dr. Thomas Cervantes, leader of the study, told BBC News. He said the accomplishment was significant for two reasons. “One — we were able to keep the shape of the ear, after 12 weeks of growth in the rat. And then secondly we were also able to keep the natural flexibility of the cartilage.”

They say the ear could be grown to help those with faces disfigured in accidents, and to help people born without ears or with ear deformities. Japan Today reports that a clinical study involving humans is expected to occur in five years. This kind of tissue engineering is being explored to grow other body parts as well, like windpipes and noses.