The Large Hadron Collider experiment has re-started after a 14-month hiatus while the machine was being repaired.
Engineers have made two stable proton beams circulate in opposite directions around the machine, which is in a tunnel beneath the French-Swiss border. The team may try to increase the £6bn ($10bn) collider's energy to record-breaking levels this weekend. The LHC is being used to smash together beams of protons in a bid to shed light on the nature of the Universe. It is the world's largest machine and is housed in a 27km-long circular tunnel. During the experiment, scientists will search for signs of the Higgs boson, a sub-atomic particle that is crucial to our current understanding of physics. Although it is predicted to exist, scientists have never found it.