View larger image | For about $1,000, anyone can buy a 3-D printer that builds objects layer by layer out of plastic. More expensive machines can handle metals, ceramics and other custom materials. The user starts by drafting an object with computer-aided design software. The machine then starts to build the object by depositing the material one layer at a time. Some machines spray or squeeze layers of liquid or powder that harden into a solid (shown). Others use heat, lasers or binders to fuse grains of loose powder into solid layers. Credit: S. Egts