The most obvious solution to packing in more computing power is to shrink the computer chip. Commercial transistors are now as small as 32 nanometers, but that's closing in on the limits of current fabrication technology.

As any city dweller knows, the way to make the most of limited space is to build up. Researchers have come up with a crossbar design for computer chips, essentially building a layer of nanowires on top of another layer of nanowires at a perpendicular angle. The intersections between the sets of wires are known as memristors, a new circuit element that can store information even after the current is turned off.

Researchers at HP have built prototype memristors, shown here, that may eventually allow computers to mimic the human brain in their ability to retain information and grow stronger with use.