Researchers are presently working on a very diverse array of methodologies for tissue engineering, seeking the technology base of tomorrow that will enable cost-effective growth of replacement tissues and organs. Here is another in its early stages: "The power of magnetism may address a major problem facing bioengineers as they try to create new tissue - getting human cells to not only form structures, but to stimulate the growth of blood vessels to nourish that growth. ... magnetic particles suspended within a specialized solution act like molecular sheep dogs. In response to external magnetic fields, the shepherds nudge free-floating human cells to form chains which could potentially be integrated into approaches for creating human tissues and organs. ... The next step is to see if the spatial arrangement of these cells in three dimensions will promote vascular formation. A major hurdle in tissue engineering has been vascularization, and we hope that this technology may help to address the problem."