BBC World Service has been following six athletes as they train to take part in the greatest sporting extravaganzas on earth.
For most competitors, the Olympics represents the pinnacle of achievement. It takes years to get there and participants have been striving for perfection for most of their lives.

Which of the hopefuls will make it to the big stage in Beijing?
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Throughout the year, Russell Fuller has enjoyed unprecedented access to the six hopefuls as they complete their difficult journeys on the long road to Beijing.
In Programme 3, the final part of this series and the Games in sight, there is huge disappointment for one, as the other five athletes build towards their peak.
Reigning Commonwealth long jump champion Ignisious Gaisah lives and trains in Rotterdam.
The Ghanian went to the Netherlands in 2001 and soon demonstrated his talent by winning every meeting he competed in. Gaisah is considered one of the best long jumpers in the world, after jumping a personal best 8.34 metres and a silver medal at the World Championships in Helsinki in 2005.
In the run up to the Games, Gaisah seriously damaged his left knee but despite heavy physiotherapy, he has lost the battle to compete in Beijing.
Sprinter Virgil Hodge is a national hero in St Kitts and Nevis. She will be competing in the 100 and 200 metres at the Olympics. She is having an outstanding year and has broken her own national 100 metres record.
Outside of athletics, Hodge engages her passion for music, she was in a pop group at school, often sings the national anthem at government functions, and does jingles for DJs on the radio.
She was told she would never run again following a back injury in early high school which almost ended her career and when she retires from the sport, she wants to work in the travel industry.
Great Britain's Sarah Stevenson will be taking part in her third Olympic Games. She was just 17-years old in Sydney when she stepped from her Doncaster classroom to finish fourth in taekwondo as the sport made its full Olympic debut; she missed the bronze by a single point.
Her status has grown hugely since then and she is now one of the favourites for gold in August.
Beijing Calling follows Sarah's progress at the Dutch Open and her ongoing treatment for a persistent foot injury and joins her in a Spanish evening class as she takes her mind off competing.
Malaysian swimmer Daniel Bego has qualified for three events but he is restrained about his expectations in the Beijing Olympics.
Daniel caught the attention of the public when he delivered three of the eight medals Malaysia won in the 2003 SEA Games in Vietnam when he was only 14 then.
Although Daniel is supposed to observe a strict diet, he has a weakness for burgers and like others his age, he is also into movies and parties. But nothing beats sleeping, which the Scarlett Johansson fan claims is a "swimmer's favourite pastime" as training can be really exhausting.
George Bovell III won a bronze medal in Athens in 2004 which was the Caribbean's first medal ever in the sport of swimming, and the only medal for Trinidad and Tobago in Athens 2004.
His father, George Bovell II, was a collegiate swimmer and mother, Barbara, was an Olympic runner for Barbados and Canada.
To take his mind off training, George regularly goes spear fishing and survived a shark attack in Florida in April.
Kenny van Weeghel is a paralympic athlete from the Netherlands who will be competing in the 100m, 200m and 400m T54 class wheelchair racing.
At the 2004 Summer Paralympics in Athens, he won three medals: bronze in the 100m, silver in the 200m and gold in the 400m. He was voted Dutch handicapped sportsman of the year.
Van Weeghel started playing basketball but later changed to racing as the "ball got in the way". Kenny loves the adrenaline rush of racing on the track and on the road gaining speeds of up to 80 km per hour.
His coach says he is notorious for being untidy and late for training.