How do you make a human ear that looks and functions like a real one? Researchers at Cornell published the first successful process in PLoS ONE Wednesday. Step 1: Take a laser scan of a real human ear. Step 2: Use digitization to print an ear-shaped collagen mold using a 3-D printer.

A collagen ear, to be seeded with living cartilage cells and implanted under skin. Image courtesy of Lindsay France/Cornell University Photography Step 3: Inject mold with gel of living cells. Step 4: Let sit in culture for three months until cartilage grows to replace collagen.

Three months after implantation, acellular implants (A) had decreased in size, whereas cellular constructs (B) retained their original anatomic fidelity. Ear B (printed and then cultured with cells) is the definite winner. Image courtesy of Alyssa J. Reiffel et al./PLoS ONE Step 5: Attach ear. (This step has yet to be tried, but scientists have high hopes for success since the use of human cells minimizes the likelihood of rejection. Also cartilage, even in a real ear, doesn't need to be connected to a blood supply to survive.)