To investigate the basic structure of matter and to find out what the particles that make up atoms are made of, scientists take those particles and smash them into each other.

In the wreckage of these tiny collisions can be found new particles that provide clues about how matter is made.

The tiny explosions recreate on a small scale what conditions were like at the start of the universe in the big bang.

Inside the LEP tunnel

The Large Electron Positron collider, LEP, near Geneva, is the world's largest sub-atomic particle collider. It consists of a giant underground tunnel 27 km long.

Circling one way around the tunnel are streams of electrons; circling the other way are positrons which are the anti-matter equivalent of electrons.

These two particle streams are brought together in detectors that analyse the debris of the collision.

LEP has already shed new light on the structure of matter and the way the various families of sub-atomic particles relate together.

Two weeks after starting its latest series of observations, LEP is operating a record breaking energies. It offers the possibility of discovering new building blocks of the universe.