What's better than 3D printing? How about 4D printing? The U.S. Army Research Office is throwing money into doing that. This video after the jump will show you why this technology is exciting.
In essence, the "fourth dimension" represents change—4D printing simply refers to printers that create objects that can transform over time and, in some cases, self-assemble.
This video, by Kinematics shows what it means. But before that, here's them explaining it:
Kinematics is a system for 4D printing that creates complex, foldable forms composed of articulated modules. The system provides a way to turn any three-dimensional shape into a flexible structure using 3D printing.
The advantage of 4D printing is that shapes can be squashed into their smallest arrangement and 3D printed economically.

Now, watch the video: [Kinematics via Boing Boing]