This unattached ear bathed in pink goo may look like a freaky find from Frankenstein’s laboratory, but it’s actually the product of a decade worth of medical research with 3-D printing.

Bioengineers from the Wake Forest Institute for Regenerative Medicine in North Carolina crafted the ear along with a jawbone, skull bone and skeletal muscle using what they call an “integrated tissue and organ printing system.” They then implanted them into mice and rats and found that the 3-D printed biological structures not only stayed alive for several months, but grew.

The team members published the blueprints behind their constructions this week in the journal Nature Biotechnology. In the past, medical researchers have created similar chunks of tissue and organ prototypes using 3-D printers loaded with live cells, but many of those prints were either structurally unfit for transplantation or unable to survive within a host.

Scientists have placed human-size ear structures into rodents before, but those ears were not 3-D printed, or did not keep their structure for long or did not grow cartilage and blood vessels as this one did.