Microchips have been given the breath of life thanks to bioengineers who microfabricated a mini device that may one day be a cheap replacement for lung-cell culture and animal models in drug development and toxicology testing. Researchers led by Don Ingber of Harvard University built their pseudolung using a microfluidic device containing a porous silicone membrane that has human epithelial cells on one side and endothelial cells on the other—in effect, re-creating the lung’s air-to-blood interface (Science 2010, 328, 1662). By applying a vacuum to select parts of the chip, the team simulates the mechanical movements that come from breathing. When they exposed their lung-on-a-chip to pathogenic bacteria and to signaling molecules, the cells in the lung model behaved as normal lung cells would, engulfing the microbe, for example. The team also exposed the lung-on-a-chip to nanoparticles. The researchers found that when the lung-on-a-chip experienced the equivalent of breathing motions, many more nanoparticles were transported from the air space to a microengineered blood vessel, and they confirmed the same response occurs in a whole lung in mice.