T. Minari, M. Kanehara, and co-workers report a method for the room-temperature printing of electronics using gold nanoparticles, enabling semiconductor devices to be printed without the application of heat. On page 4886, organic thinfilm transistors are formed on plastic and paper through room-temperature printing, producing devices with mobilities of 7.9 and 2.5 cm2 V−1 s−1, respectively. The proposed approach permits the printing of devices on any heat-sensitive substrate, such as plastic, paper, or biomaterials.