The audiences at TED talks are used to being wowed as they learn about advances in technology. Even by TED standards, however, the 2011 presentation by Anthony Atala of the Wake Forest Institute for Regenerative Medicine was amazing. Unseen by the audience at first, various vials and nozzles hummed with mysterious activity behind Atala while he was on the stage. About two thirds of the way through the talk, a camera zoomed in on the device's internal armature and showed it weaving back and forth, depositing living cells grown in a laboratory culture layer by layer on a central platform, basing its activity on highly accurate three-dimensional digital renderings. The process, known as 3-D printing, resembles the operation of ink-jet printers but, in this case, instead of ink the printer uses a solution of living cells. In the end, Atala's machine produced, layer by layer, a life-size kidney made of human cells, much as a personal 3-D printer can spit out, say, a plastic replacement part for a coffeemaker.