Mr Spievak re-grew his finger tip. He used a powder - or pixie dust as he sometimes refers to it while telling his story.
Mr Speivak's brother Alan - who was working in the field of regenerative medicine - sent him the powder.
For ten days Mr Spievak put a little on his finger.
"The second time I put it on I already could see growth. 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."
It's been known for years that children under 11 who lose a fingertip will regrow it if the wound is left open, but this is the first time the process has been induced in an adult (or in anyone of any age). The scientists behind the "pixie dust" say organ and limb regeneration could be a possibility.
Here's a link to the BBC's article about Spievak's new digit, including a video with images of the finger as it grew back.