An artificial - and very lifelike - ear has been built by scientists using a 3D printer and cartilage from sheep.
The organ was designed by plastic surgeons to make it look as likelike as possible.
Researchers from Massachusetts then grew the required number of cartilage cells to fit custom models under the skin of lab rats.
Wire was added to the moulds to give the implants their shape and make them bend and flex like human ears.
Scientists are now preparing the ear for clinical trials in the hope they could be used in transplant operations.
As the technology is customisable, the scientists claim they could eventually use the process to produce realistic looking ears for individual patients on a 'rapid timescale.'
The ears were built by Thomas Cervantes, from Massachusetts General Hospital, and his colleagues.
A 3D digital model was created and designed with help from a facial plastic surgeon to make sure the shape and proportions were correct.
The resulting model was printed and cast in polydimethylsiloxane, a special silicone compound, to create a mould which was then split along the outer contour, resulting in two pieces.
These moulds were filled with cow collagen, the naturally occurring protein that gives skin elasticity and strength.
Researchers then harvested ear cartilage cells from sheep.
These cells were implanted under the skin of lab rats and the team then spent three months growing enough cartilage inside the rats to replace the cow collagen used in the moulds.
The researchers said that the modelled ear had enough definition in the curves and lines to be recognisable even once a layer of skin had been applied to it.
'All the implants were well tolerated,' said Cervantes.
'The implants with wire resembled a human ear, whereas implants without wire were flattened and distorted.
'The surfaces of both were white, glistening and grossly resembled cartilage.
'The constructs with the embedded wire framework had significantly improved size and shape fidelity, compared with those without the framework. The implants were flexible.'
The same team previously carried out a proof of concept study on mice using cartilage cells in an ear-shaped collagen mould, but this was only analysed in 2D.
The researchers said: 'The technology is now under development for clinical trials, and thus we have scaled up and redesigned the prominent features of the scaffold to match the size of an adult human ear and to preserve the aesthetic appearance after implantation.
'We also employed more rigorous methods to analyse the fidelity of the ear geometry after implantation.'
They added: 'These quantitative shape analysis results have identified opportunities to improve shape fidelity of engineered ear constructs.'
Each year thousands of children are born with a congenital deformity called microtia, when the external ear is not fully developed.
Many have an intact inner ear, but experience hearing loss due to the missing external structure.
The findings feature in the Journal of the Royal Society Interface.