Rock in your pocket (no. Not that kind)

For the director of Massachusetts Institute of Technology's gas turbine laboratory, the fascination has to do with raw power. "The engines on three 747s put out as much power as a nuclear power plant," Epstein says.

These days it isn't the hulking machines that capture Epstein's enthusiasm. Instead, it's a jet engine shrunk to about the size of a coat button that sits on the corner of his desk. It's a Lilliputian version of the multi-tonne jet engines that changed air travel and, he believes, could be the key to powering the 21st century.

Although the turbine's blades span an area smaller than a five-cent piece, they spin at more than a million revolutions a minute and are designed to produce enough electricity to power hand-held electronic equipment.

Epstein expects his tiny turbines will serve as a battery replacement, first for soldiers and then for consumers. But he has an even more ambitious vision: that small clusters of the engines could serve as household generating plants. The technology could be especially useful in remote areas.

Hooray for small turbines.