(From Delaware Online). Researchers continue to explore the boundaries of regeneration: how much or how little will we have to do to convince human biochemistry to regrow digits and limbs? "It sliced off his fingertip, leaving just a bit of the nail bed. The missing piece, three-eighths of an inch long, was never found. ... Spievack, however, did have a major advantage - a brother, Alan, a former Harvard surgeon who'd founded a company called ACell Inc., that makes an extract of pig bladder for promoting healing and tissue regeneration. ... Within four weeks his finger had regained its original length, he says, and in four months 'it looked like my normal finger.' ... it's not completely clear what happened inside Lee Spievack's finger. The broad outline is pretty straightforward. The powder is mostly collagen and a variety of substances, without any pig cells ... It forms microscopic scaffolding for incoming human cells to occupy, and it emits chemical signals to encourage those cells to regenerate tissue ... we are very uninformed about how all of this works. There's a lot more that we don't know than we do know." This is one end of a broad spectrum of work presently taking place - interesting results will come in the years ahead.