Every year, about 22,000 transplants are performed in the U.S. But supply of organs is limited, and thousands die waiting for a transplant. A possible solution: bioprinting, which builds on 3-D printing technology that’s already used in many industries. How does it work? Bioprinters use multiple print heads to spray out a person’s own cells, along with chemical binding agents that help hold the cells together. Layers of cells then grow into living, functional tissue that can be implanted. The technology has already been used on animals to implant printed ears, bones, and muscles. Experts hope the first printable tissue for humans will be ready to transplant in a few years. One advocate, Dr. Frank Rybicki in Ottawa, Canada, predicts the technology will be a huge medical leap. “When bioprinting actually hits,” he says, “it will change everything.”