The Large Hadron Collider has successfully created a "mini-Big Bang" by smashing together lead ions instead of protons.
The scientists working at the enormous machine on Franco-Swiss border achieved the unique conditions on 7 November.
The experiment created temperatures a million times hotter than the centre of the Sun.
The LHC is housed in a 27km-long circular tunnel under the French-Swiss border near Geneva.
Up until now, the world's highest-energy particle accelerator - which is run by the European Organization for Nuclear Research (Cern) - has been colliding protons, in a bid to uncover mysteries of the Universe's formation.
The LHC is smashing together particles in a bid to unlock the secrets of formation of our Universe
It is operated by the European Organization for Nuclear Research (Cern) in Geneva
The collider is housed in a 27km-long circular tunnel under the French-Swiss border
The giant tunnel is located an average of 100m underground
The LHC is the world's largest and highest-energy particle accelerator
The circumference of the LHC is 26 659 m, with a total of 9300 magnets inside
The magnets are cooled to an operating temperature of -271.3°C (1.9 K) - colder than deep space
Large Hadron Collider: A Guide
Proton collisions could help spot the elusive Higgs boson particle and signs of new physical laws, such as a framework called supersymmetry.
But for the next four weeks, scientists at the LHC will concentrate on analysing the data obtained from the lead ion collisions.
This way, they hope to learn more about the plasma the Universe was made of a millionth of a second after the Big Bang, 13.7 billion years ago.
One of the accelerator's experiments, ALICE, has been specifically designed to smash together lead ions, but the ATLAS and Compact Muon Solenoid (CMS) experiments have also switched to the new mode.
David Evans from the University of Birmingham, UK, is one of the researchers working at ALICE.
He said that the collisions obtained were able to generate the highest temperatures and densities ever produced in an experiment.
"We are thrilled with the achievement," said Dr Evans.
The ALICE experiment has been designed specifically for lead ion collisions
"This process took place in a safe, controlled environment, generating incredibly hot and dense sub-atomic fireballs with temperatures of over ten trillion degrees, a million times hotter than the centre of the Sun.
"At these temperatures even protons and neutrons, which make up the nuclei of atoms, melt resulting in a hot dense soup of quarks and gluons known as a quark-gluon plasma."
Quarks and gluons are sub-atomic particles - some of the building blocks of matter. In the state known as quark-gluon plasma, they are freed of their attraction to one another. This plasma is believed to have existed just after the Big Bang.
He explained that by studying the plasma, physicists hoped to learn more about the so-called strong force - the force that binds the nuclei of atoms together and that is responsible for 98% of their mass.
After the LHC finishes colliding lead ions, it will go back to smashing together protons once again.
Source BBC NEWS