One of London 2012's aims is to leave a legacy for the next generation. Here's some of this year's stars when they were young.
Staying with tennis, here are Venus and Serena Williams in 1990 with former President of the United States Ronald Reagan. The superstar sisters made Olympic history becoming the first pair to win the women's doubles three times. Serena also won her first singles title.
London 2012 organisers say they want the Games to inspire the next generation. Here is Tom Daley aged 13. Our top diver narrowly missed out on a medal in the men's synchronised 10m platform, but he goes for gold again on Thursday in the individual event. Nice braces Tom!
Here is British Olympic 10,000m champion Mo Farah, aged 19, pictured in 2002. Mo crossed the line in London in 27 minutes 30.42 seconds becoming one of the heroes of the Olympics.
Here's heptathlete Jessica Ennis, aged 17. She says she always dreamed about winning gold at the Olympics. But back then she couldn't have known she was going to become the biggest name in athletics at a home Games! Her gold is one of the big highlights of 2012.
Here's the most famous swimmer ever, American Michael Phelps, aged 14. He's become the most successful Olympian in history. At London 2012, his medal haul rose to 22, with 18 of them gold.
Would you like to be an Olympic gold medallist when you grow up? Well here are some famous London 2012 sportsmen and women when they were young! This is Andy Murray in 1999. He beat Roger Federer in this year's Olympic final to get the tennis gold medal.
Last up, no prizes for guessing who this super-speedy sprinter is. It's two-time 100m Olympic champion and world record holder Usain Bolt, pictured in 2002. Bolt stormed the Beijing Games in 2008 getting victory in the 100m, 200m and 4x100m relay. This year he's got the 100m, but how many more golds will he win?