Newsround looks at the history of the Olympic torch, where the idea for the relay started and some of the unusual designs.
Sometimes the Olympic flame goes out, so organisers carry a back-up flame kept in an Olympic lantern. This one is from the 2002 Salt Lake City relay.
The Olympic flame was lit in Greece this week after a fancy, traditional ceremony to mark the start of the torch relay but where did the tradition come from?
After the Second World War the idea of a torch relay returned for the 1948 Olympic Games in London. It was known as the 'relay of peace'.
Every year the torch became a little more fancy as the organisers tried to out-do the previous host. This torch from Rome in 1960 shows the designs getting a little more lavish.
Organisers of the 1984 games in the US went for a more traditional design with posh gold trim.
The organisers of the Mexico City Olympics in 1968 chose this fancy design but it exploded shortly after this photo was taken and injured both athletes!
The Olympic flame originated in ancient Greece, where a fire was kept burning throughout the celebration of the ancient Olympics. But the first torch relay was organised in Germany by the Nazi Party for the 1936 Olympic Games in Berlin.
Here's the torch from 1948 which is going on sale in July 2012.
This year's torch has 8,000 holes - one to represent each torch bearer for the 70-day relay. Here it is just after being lit at a ceremony in Greece. Bring on the Games!
This torch from Greece in 2004 looks more like a flask of coffee than an Olympic flame but it did the job beautifully.
Check out this swirly torch from the 2008 Beijing Games which looks like a curled up scroll. Luckily, the organisers had the foresight to make it out of metal and not paper.
This modern design from 2000 resembles the famous Sydney Opera House in Australia. That year's relay started at Uluru in the Australian desert.