Larry L. Miller is still astonished by the notion of measuring individual molecules.

"As I was saying to a lawyer friend the other day, observing single molecules and measuring their length is like taking a picture of the world, then trying to pick out one individual human being -- they look a lot like the background dirt and rocks -- measuring him at 5 feet 10 and comparing him to his neighbor at 5 feet 8," Miller said.

"To do that you'd have to paint their heads and feet so you could measure the difference in the picture," he said.

That is what chemist Miller and his colleagues at the University of Minnesota said they have done with molecules.

In a report in the January 20 issue of the Journal of the American Chemical Society, Miller described the molecular ruler that his group and one at the Brookhaven National Laboratory have made.

Tiny electronic devices are already measured on a scale of micrometers, or millionths of a meter. But to step into a future in which supercomputers are the size of sugar cubes -- with incredibly tiny wires and connections -- it is necessary to measure and manipulate objects the size of individual molecules.

Miller and his group have developed a method of measuring things down to the level of less than a nanometer, or a billionth of a meter -- the size of an atom.

They use clusters of iridium atoms, which are highly visible as spots under a scanning transmission electron microscope. These clusters are attached at either end of rod-shaped molecules.

So far, Miller's group has measured lines between two and four nanometers in length. He said he expects soon to have an iridium measuring stick that can be accurate down to two-tenths of a nanometer.

Miller said that in practical uses, the iridium might be chemically attached to the ends of lines or wires on a tiny electronic device to see if they are the right length.