Deep in a dim cavern, UCLA physicist Bob Cousins scrambled onto a catwalk straddling the six-story detector known as the Compact Muon Solenoid, then darted up two flights of stairs to another catwalk, where the guts of the machine materialized out of the half-light.
It looked a little like the inside of a computer suffering from a severe case of gigantism. Plates, shields and pipes jutted everywhere. Thick knots of cable extended from the side like mounds of heavy rope on an 18th century whaling ship.
"This detector was assembled at the surface and lowered in 15 pieces," Cousins said, pointing to a wide opening above the detector that reached to the European sky high above.
The heaviest piece weighed 4 million pounds. It took 10 hours to lower the middle section. At the center of this section is a bulbous extension that makes the behemoth look like the world's biggest television picture tube. This single piece of the collider contains more iron than the Eiffel Tower.
It was all built to probe a beam of particles thinner than a blade of grass.
Decades ago, scientists figured out that atomic nuclei were made up of smaller things than protons and neutrons.
To find those pieces, 20th century physicists came up with an idea that would appeal to most 9-year-old boys with a new toy: "Let's smash it and see what happens."
Early colliders, like the 9-inch cyclotron created at UC Berkeley in 1931, sent particles down a circular drag strip and crashed them into a target to see what flew out.
From there, particle physics exploded. Larger and more sophisticated devices kept packing more energy into the colliding particles, allowing scientists to peer deeper into the guts of the atom.
Protons and neutrons, they found, were made up of even smaller particles, dubbed quarks, which were bound together by another set of particles, called gluons. Gluons were part of a larger family, bosons, each of which carries some form of force. Photons, which make up light, for example, carry the electromagnetic force.
They found a bestiary of particles -- pions, kaons, deltas and other exotically named objects -- that existed beyond an atom's nucleus.
Altogether, scientists found dozens of species of elementary particles, some composed of pieces so tiny that they make an atom look like a sumo wrestler, or a mountain. If a quark measured an inch, an atom would stretch at least 1,000 miles, about the distance from Los Angeles to Denver.
