CERN is an organisational headquaters of scientists, based in Switzerland, which houses a large hadron collider (the LHC). By smashing particles together at great speed, it's hoped that the LHC will be able to recreate the conditions present at the beginning of the universe (the big bang). The scientists are examining the microscopic collisions, which are created by shooting atoms around the huge tunnels of the LHC. Please also see this article for further easy to understand information about CERN: http://scientificinquiry.suite101.com/article.cfm/cern_the_big_bang_machine