However, in the last several years, 3D printers have become increasingly common. The technology is still in its infancy, but companies have already performed demonstrations by, for instance, printing words on a substrate using individual atoms. This is seen by some as the beginning of the beginning for real, practical, self-assembling manufacturing systems. A printer can build more printers, robotic workers, miners, and ultimately more Von Neumann machines. A few companies are experimenting with print heads capable of delivering multiple materials, kind of like color inkjet printers. The technology should continue to improve, until they have something that can deliver any element, atom by atom.