The world's largest atom smasher, the Large Hadron Collider, was poised to start a new era of science, colliding beams of protons to learn more about the make-up of the universe and its smallest particles.
Two beams of protons began 11 days ago to speed at high energy in opposite directions around the Collider under the Swiss-French border in Geneva.
The beams have been pushed to 3.5 trillion electron volts, the highest energy achieved by any physics accelerator - some three times greater than the previous record.
The European Organisation for Nuclear Research, or CERN, plans to start trying to use the powerful superconducting magnets to force the two beams to cross, creating collisions and showers of particles.
They could be successful immediately, but such huge machines can be so tricky to run that it could take days.
The beams will be packed with hundreds of billions of protons, but the particles are so tiny that few will collide at each crossing.
Dubbed the world's largest scientific experiment, the £6.7 billion Large Hadron Collider holds the promise of revealing details about theoretical particles and microforces, scientists say.
Steve Myers, CERN's director for accelerators and technology, describes the challenge of lining up the beams as being akin to "firing needles across the Atlantic and getting them to collide half way".
The collisions will come over the objections of some people who fear they could eventually imperil Earth by creating micro black holes -- sub-atomic versions of collapsed stars whose gravity is so strong they can suck in planets and other stars.
CERN and many scientists dismiss any threat to Earth or people on it, saying that any such holes would be so weak that they would vanish almost instantly without causing any damage.