Despite being able to build just about anything with 3D printing, until now items have been limited to polymer plastics, a handful of metals and glass. However, researchers at HRL Laboratories have announced a significant advancement in additive manufacturing: the ability to print ceramics. The trick, the HRL team figured out, was to not heat ceramic powder. Doing so generates too many microscopic flaws that can lead to cracks and fractures. Instead, the team developed a material they're calling "preceramic polymers" that convert to ceramic when heated. Essentially, the HRL team prints out the 3D design using these preceramic polymers and then fires the resulting item (like in a kiln) to harden the material into ceramic.