In the world of nanotechnology, which is measured in molecules, engineers crafted some nifty miniature machinery this year. Different teams created the world's smallest car refrigerator and fountain pen . One hope is that these tiny machines, invisible to the human eye, will one day be used to deliver drugs into cells, perhaps to destroy cancer or cure other ills. Technology tasks are envisioned too. In one nifty breakthrough, researchers merged microbe and machine for the first time, creating gold-plated bacteria that sense humidity.

Using the parts inside a single molecule, scientists have constructed the world's smallest car. It has a chassis, axles and a pivoting suspension. The wheels are buckyballs, spheres of pure carbon containing 60 atoms apiece.

It'd be a real squeeze to take it for a spin, however.

The whole car is no more than 4 nanometers across. That's slightly wider than a strand of DNA. A human hair is about 80,000 nanometers thick.

Other groups have made car-shaped nanoscale objects. But this is the first one that rolls "on four wheels in a direction perpendicular to its axles," the researchers reported Thursday.

What's the point? Nanotrucks, of course.

Eventually the researchers want to build tiny trucks that could carry atoms and molecules around in miniature factories.

"We'd eventually like to move objects and do work in a controlled fashion on the molecular scale, and these vehicles are great test beds for that," said James Tour, a Rice University research who co-led the work. "They're helping us learn the ground rules."

The setup will be detailed in an upcoming issue of the journal Nano Letters.

The scientists had to use "scanning tunneling microscopy" to see the thing and prove that it rolls like a car.

"It's fairly easy to build nanoscale objects that slide around on a surface," said Tour's colleague Kevin Kelly. "Proving that we were rolling – not slipping and sliding – was one of the most difficult parts of this project."

So just how do you make a nanocar go?

At room temperature, strong electrical bonds hold the buckyball wheels tightly against the gold, but heating to about 200 degrees Celsius frees them to roll.

The breakthrough is one of many recent successes in the world of the very small: