Engineers operating the Large Hadron Collider (LHC) have smashed together proton beams in the machine for the very first time.
The low-energy collisions came after researchers circulated two beams simultaneously in the LHC's 27km-long tunnel earlier on Monday.
The LHC is smashing together beams of protons to shed light on the cosmos. Operated by the European Organization for Nuclear Research (Cern), the LHC is the world's largest machine and will create similar conditions to those present moments after the Big Bang.
Scientists will search for signs of the Higgs boson, a sub-atomic particle that is crucial to our current understanding of physics. Although it is predicted to exist, scientists have not yet detected it.
"This is great news, the start of a fantastic era of physics and hopefully discoveries after 20 years' work by the international community."
-Fabiola Gianotti, spokesman for the Atlas scientific team
Housed in a tunnel 100m beneath the Franco-Swiss border, the LHC uses some 1,200 "superconducting" magnets to bend proton beams in opposite directions around the tunnel at close to the speed of light.
At allotted points around the "ring", the proton beams cross, smashing into one another with enormous energy.
Large "detector" machines located at these crossing points will scour the wreckage of the collisions for discoveries that could roll back the frontiers of knowledge.
Engineers restarted the LHC on Friday evening after a 14-month hiatus while the machine was being repaired.
It had to be shut down shortly after its inauguration when an electrical fault led to magnets being damaged and to one tonne of liquid helium leaking into the tunnel.