CERN was a scientific establishment in Switzerland. It housed the Large Hadron Collider, which allowed Neutron eaters to escape into N-Space and kill humans. Torchwood Three, along with some CERN staff and UNIT's Martha Jones, managed to defeat the neutron eaters and save CERN. (AUDIO: Lost Souls)
Liz Shaw left UNIT to go work for the then-new organisation. (PROSE: Country of the Blind)