Scientists at the European Organisation for Nuclear Research in Switzerland have re-started the giant sub-atomic particle collider in a tunnel beneath the French-Swiss border.
The Large Hadron Collider is designed to smash together beams of protons in a bid to shed light on the nature of the Universe and the fundamental nature of matter, the BBC reports.
The collider will create similar conditions to those present moments after the Big Bang. It had been shut down for repairs since September 2008 due to a series of technical faults.
Engineers working on the machine achieved a stable, circulating proton beam in the 27km-long tunnel just after 9pm (GMT) on Friday.