The particle collider that gave scientists a glimpse of what may be the Higgs Boson shut down Thursday for a two-year revamp that will allow it to pursue the quest with renewed vigour.
The Large Hadron Collider (LHC), straddling the border between France and Switzerland, has been working non-stop for three years to find the elusive "God Particle".
The boson is theorised to explain the mysteries of mass.
The European Organisation for Nuclear Research (CERN), which operates the collider, said its crew began winding down the vast facility just after 7:00 am (0600 GMT) on Thursday.
It is due to go completely offline on Saturday.
"We have every reason to be very satisfied with the LHC's first three years," CERN's director general, Rolf Heuer, said in a statement.
"The machine, the experiments, the computing facilities and all infrastructures behaved brilliantly, and we have a major scientific discovery in our pocket."
The LHC smashes invisible particles together to better understand the micro-moment after the creation of our Universe some 14 billion years ago.
British physicist Peter Higgs theorised in 1964 that the boson could be what gave mass to matter as the Universe cooled after the Big Bang.
Located in a 26.6-kilometre (16.5-mile) circular tunnel, the LHC was the scene of an extraordinary discovery announced in July 2012.
CERN's scientists said they were 99.9 percent certain they had found the Higgs Boson, an invisible particle without which, theorists say, humans and all the other joined-up atoms in the Universe would not exist.
At a cost of up to 50 million Swiss francs (40 million euros/$54 million), the upgrade will boost the level of energy at which the LHC smashes protons together.
This is necessary to confirm definitively that its particle is the elusive Higgs, and allow the LHC to probe new dimensions such as supersymmetry and dark matter.
The LHC is due to be back online by 2015, but CERN will not be idle during the shutdown.
Its scientists have to sift through a vast mountain of data, equivalent to 700 years of full HD-quality movies.