The Large Hadron Collider (LHC) is based 100 meters below ground, with a circumference of 27 km, and is operated from the control room of the European Organisation for Nuclear Research (CERN). (Image gallery)
During the test, a beam of protons completed a clockwise lap of the accelerator ring, in extreme vacuum cooled by liquid helium to minus 271 degrees C.
Lyn Evans, LHC project leader, called the test-run conducted at 9:30 a.m. (07:30 GMT) a "fantastic moment" hailing a new era in scientists' understanding of the universe.
Later, sub-atomic particles will be sent round the accelerator ring in opposite directions at almost the speed of light, guided by a powerful magnetic field produced by superconductor magnets, and will collide in front of huge particle detectors.
Many scientists hope the experiment will reveal the Higgs boson, nicknamed the "God particle", a concept hypothesized in the 1960s to explain how particles acquire mass.
British astrophysicist Stephen Hawking earlier told the BBC he had bet colleagues 100 dollars that the elusive particle will not be found.
"I think it will be much more exciting if we don't find the Higgs. That will show something is wrong, and we need to think again. I have a bet of 100 dollars that we won't find the Higgs," he said.
Discovering the particle could explain how, in the split-second after the Big Bang, matter appeared from nothingness.
The international LHC project has involved more than 2,000 physicists from hundreds of universities and laboratories in 34 countries since 1984. Over 700 Russian physicists from 12 research institutes have taken part.
Prof Frank Wilczek of MIT has called the experiment "our civilization's answer to the Pyramids of Egypt."
Ahead of the test, LHC Russian coordinator Viktor Savrin said unless the Higgs boson is found, no larger device would ever be built.
"I do not think it is realistic to build a larger accelerator on a similar scheme, nobody is likely to venture to do that," Savrin said.
