There was an article in the Herald last week (I think) which set my pseudoscience detector ringing… it had a title something like "Pixie dust helps man regrow finger". The article itself gushed on about how this guy had lost part of his finger to a bit of sharp-edged machinery, but the missing bit – including even the nail & fingerprint, raved the article's author – had regrown following application of a non-cellular matrix whimsically called 'pixie dust'…
Humans really aren't too good at regenerating missing parts, so if this one was for real then the 'pixie dust' is an amazing scientific discovery. (It sounds like it's made from the collagen & other proteins left when pigs' bladders have all the cellular parts of their structure removed.) But in fact, it turns out to have been totally overblown by the media. And there hasn't been a formal paper in a scientific journal that describes the properties & powers of the 'pixie dust' matrix, either. And it's apparently an old story, as a bit of ferreting around by Ben Goldacre has shown.
For a start, despite media claims that a missing finger or substantial part thereof had regrown, in fact the patient seemed to have lost around 1cm off the top of a finger – skin & flesh, but not (from looking at the available images) any bone – leaving the nail bed intact. So it's no surprise that the nail would regrow. The rest of the 'regrowth' looks (again, from the available images, of which there are surprisingly few) like normal healing & scarring. And as anyone who's had a cut, graze, burn or scrape knows, this sort of healing happens all the time, without the need for any 'magical' intervention.
It's been said before: extraordinary claims require extraordinary evidence.