The world's tiniest machines measure only one-thousandth the thickness of a human hair, but they stand to play a big role in our nanotech-enabled future.

So reckons the committee behind this year's Nobel Prize in Chemistry, which was awarded on Wednesday to a trio of scientists whose deft manipulations have opened the door to a world of miniature motors, switches, pumps and other devices all at the scale of individual molecules.

Jean-Pierre Sauvage, 71, of the University of Strasbourg in France, and Sir J. Fraser Stoddart, 74, a Scottish-born researcher based at Northwestern University in Evanston, Ill., will split half of this year's chemistry prize, worth about $1.2-million. The other half has been awarded to Bernard Feringa, 65, of the University of Groningen in the Netherlands.

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All three scientists made key contributions to the field of molecular machines, in which versatile chains of carbon and other atoms are assembled into Tinkertoy-style structures that can move and perform a wide range of functions.

"They have really mastered motion control at the molecular scale," said Olof Ramstrom, a professor of chemistry at the Royal Institute of Technology in Stockholm and a member of the Nobel committee.

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The committee said the three researchers deserved recognition for their contributions to the field in three distinct steps.

First, in 1983, Dr. Sauvage and his colleagues forged two rings of carbon atoms into an interlocked pair, like links in a chain, called a catenane. Then, in 1991, while at the University of Birmingham, Dr. Stoddart revealed how to make rotaxane, a structure that involves a ring of atoms that can rotate freely around an axle. Finally, in 1999, Dr. Feringa developed the first molecular motor. Together with colleagues, he more recently built a working "nanocar" propelled by electrical impulses.

Dr. Stoddart spent three years at Queen's University in Kingston, Ont., as a National Research Council Postdoctoral Fellow after completing his PhD in Scotland in 1966.

"I'm a bit shocked. … It was such a great surprise. I am so honoured," said Dr. Feringa, who was contacted by phone during the prize announcement.

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He said it is still "early days" in terms of finding practical applications for the tiny machines, but he added that "once you are able to control movement, you can think of all kinds of functions."

Researchers have long envisioned molecule-sized devices that can be injected into the bloodstream to seek out cancer cells or deliver drugs to their targets. Other machines might be used in the development of miniature computers or in smart materials that react to changes in the environment.

Stephen Loeb, a chemist at the University of Windsor whose research includes developing solid-state materials that incorporate molecular machines, said all three of the new Nobel laureates deserve credit for their technical prowess and their creativity in dreaming up the minuscule devices.

"That's the fun part," Dr. Loeb said.

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He added that the field is still waiting for the "magic app" that would move molecular machines into everyday use.

Meanwhile, the concept of molecule-size machines has spawned a rich banquet of science-fiction scenarios, not all of them benign. For example, in his 2002 novel Prey, author Michael Crichton explores the potential risk of tiny self-replicating nanobots developing a collective intelligence and threatening humankind.

However, Dr. Loeb said such portrayals are misguided. Molecular machines today are analogous to the earliest motors and electrical devices of the 19th century, which later evolved into the sophisticated machinery that enabled 20th-century mass transportation and production.

"Humanity controls macroscopic machines," he said. "I don't see any reason why we won't be able to control nanomachines."