That's the vision of a team of researchers at the Massachusetts Institute of Technology's Media Lab. With backing from General Motors Corp., they are building a prototype of a lightweight electric vehicle that can be cheaply mass-produced, rented by commuters under a shared-use business model, and folded and stacked like grocery carts at subway stations or other central sites.

It's called the City Car, and the key to the concept lies in the design of its wheels. Dreamers have been reinventing the wheel since the days of cave dwellers. But the work underway in "the Cube," the Media Lab's basement studio, may be the most ambitious remake yet.