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.