Lee Spievak, 69, severed half an inch from his fingertip after getting it caught in the propellor of a model plane.
But over four months he watched as a perfectly-formed replacement grew from his stump, complete with tissue, nerves, nail, skin, and fingerprint.
Doctors now hope that the treatment - using a powder called extra cellular matrix - could be used to repair severely burnt skin, or even damaged organs.
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Mr Spievak, who works in a hobby shop in Ohio, was unable to find his severed fingertip and doctors told him he had lost it for good.
His brother Alan, who works in the field of regenerative medicine, sent him the powder, which Mr Spievak calls 'pixie dust'.
For ten days he put a little on the end of his finger, and says after just two applications the re-growth was already visible.
He told BBC News: “Each day it was up further. Finally it closed up and was a finger. It took about four weeks before it was sealed.”
Now he says he has “complete feeling, complete movement”.
The inventor of the powder, Dr Stephen Badylak from the University of Pittsburgh, has pioneered a process which involves scraping cells from the lining of a pig’s bladder.
The tissue is then “cleaned” of all cells in acid and dried out before being turned into sheets, or a powder.
Scientists believe that when the extra cellular matrix is put on a wound, it stimulates cells in the tissue to grow rather than a scar.
Dr Badylak said: “I think that within ten years that we will have strategies that will re-grow the bones, and promote the growth of functional tissue around those bones. And that is a major step towards eventually doing the entire limb.”
The US military is poised to start trials of the powder to regrow parts of the fingers of injured soldiers.
Another trial in Buenos Aires will involve a woman who has cancer of the oesophagus.
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