Lopez Lomong: Sudan's lost boy
6 August 2012 Last updated at 17:35 BST
Olympic athletes have to go through many trials to get to the Games - but none more so than Lopez Lomong.
He was one of the so-called Lost Boys, thousands of child refugees caught up in Sudan's civil war, before he moved to the United States as part of a government resettlement programme.
On Wednesday, Lopez Lomong will represent the US in the 5,000 metre race at the 2012 Olympics.
Leana Hosea heard his story.