The Large Hadron Collider is about to start the work that could lead to the discovery of fundamental new physics, BBC reported.
Scientists working on the European machine will later attempt to smash beams of proton particles together at unprecedented energies.
The seven-trillion-electronvolt (TeV) collisions will initiate 18-24 months of intensive investigations at the LHC.
Scientists hope the study will bring novel insights into the nature of the cosmos and how it came into being.
But they caution that the data gathered from the sub-atomic impacts will take time to evaluate, and the public should not expect immediate results.
"Major discoveries will happen only when we are able to collect billions of events and identify among them the very rare events that could present a new state of matter or new particles," said Guido Tonelli, a spokesman for the CMS detector at the LHC.
"This is not going to happen tomorrow. It will require months and years of patient work," he told BBC News.
The LHC is one of the biggest scientific endeavours ever undertaken.
Housed in a 27km-long tunnel under the Franco-Swiss border near Geneva, the LHC will collide particles travelling at close to the speed of light.
The expectation is that previously unseen phenomena will reveal themselves in the debris. A key objective is to find the much talked-about Higgs boson particle.
This is thought to have a profound role to play in the structure of the Universe, and would enable scientists to explain why matter has mass - something which, at a fundamental level, they have difficulty doing at present.
The LHC broke down shortly after its opening in 2008, but since coming back online late last year has gradually been ramping up operations.
Two proton particle beams have been circling in opposite directions in the magnet-lined tunnels at 3.5 TeV since 19 March.
Having established their stability, these beams will now be allowed to cross paths and collide on Tuesday. This 7 TeV event will be the highest energy yet achieved in a particle accelerator.
In the coming months, the LHC's four major experiments - its giant detectors Alice, Atlas, CMS and LHCb - will probe the collisions.
"This is new territory," said Professor Tonelli.
"If you want to discover new particles, you have to produce them; and these new particles are massive. To produce them, you need higher energies. For the first time [on Tuesday], we will be producing particles that have energy 3.5 times higher than the maximum energy achieved so far.
"This is why we can start the long journey to make major discoveries in indentifying a new massive state of matter."
At the end of the 7 TeV (3.5 TeV per beam) experimental period, the LHC will be shut down for maintenance for up to a year. When it re-opens, it will attempt to create 14 TeV events.