How to catch Olympics cheats
- 5 July 2012
In just few weeks, the world's top athletes will come together for the biggest sporting event on Earth - the Olympics.
To make sure the competition is fair, competitors will be tested to make sure they haven't taken drugs to improve their performance.
One group of children won a competition to take a look at the science labs where the tests will be done.
Rosie and Megan took Newsround on an exclusive tour.