Proponents of 3-D tissue engineering say there's very little point in growing tissue in a 2-D petri dish, because the human body isn't flat and that experimental platforms need to emulate the body's structure more closely, reports Technology Review's Christopher Mims. To that end, a Houston-based company called n3D Biosciences has developed a new technology that uses magnetism to float cells in a 3-D matrix, Mims says. The company uses a proprietary mix of nanoparticles that, when added to a dish of living cells, "allows them to move in response to magnetic fields that can be varied in three dimensions and across time," he adds. The researchers who presented the work at a meeting of the Tissue Engineering International & Regenerative Medicine Society say their "BioAssembler" technology can levitate cells rapidly to form 3-D cell structures.