Last updated at 07:35

How to catch Olympics cheats

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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.