SMALL BLOOD VESSELS UNDER A MICROSCOPE look strikingly similar to cotton candy. So observed graduate student Leon Bellan while working with plastic surgeon Jason Spector on a major problem involving tissue engineering: A skin graft often dies because it can’t generate blood vessels quickly. The two researchers and their team at Weill Cornell Medical College in New York City and the Cornell University College of Engineering in Ithaca, N.Y., used a cotton candy machine to make the wispy treat, then coated it in a polymer and dissolved the sugar, leaving behind a microchannel network that could serve as scaffolding on which to grow tissue implants.