Jem Stansfield on how the LHC works
14 February 2013 Last updated at 17:44 GMT
The Large Hadron Collider (or LHC) is being switched off for repairs.
It's the world's biggest experiment - to try to help us understand more about the origins of the Universe.
It exists 100m below ground in a 16-mile-long tunnel on the border between France and Switzerland.
Jem Stansfield from Bang Goes The Theory explains how the LHC works.