Thousands of scientists have spent more than a decade building the Large Hadron Collider at the European Centre For Nuclear Research in Geneva.
By smashing atoms together, the machine will recreate the conditions just after the 'Big Bang' when the universe was created.
British scientist Mike Lamont, who helped build the experiment, told Sky News: "By going back in time, by recreating, we're exploring the physics, the way the universe unfolded in those first few instances of time.
"It is just part of this adventure of man pushing at the limits."
The machinery is housed in a 17 mile tunnel 100 metres beneath Switzerland and France.
Atoms will race around at virtually the speed of light in an atmosphere colder than outer space.
The millions of collisions will create temperatures 100,000 times hotter than the sun.