Thousands flocked to London's Olympic Park on Friday for the spectacular opening ceremony heralding the start of the 2012 Games.
Seven years of planning were culminating in a breathtaking £27m show devised by Slumdog Millionaire director Danny Boyle.
At the end of the three-hour ceremony, the Queen will declare open the Games of London and the Olympic cauldron will be lit.
The ceremony comes at the end of a day that has seen the Olympic torch complete its 70-day odyssey around the British Isles.
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Bells also rang out across the UK as the final countdown to the start of the 2012 Olympics began.
Big Ben was joined by hundreds of churches across the nation as it chimed non-stop for three minutes to ring in the Games.
The Prime Minister said the country would show the world "the best of Britain" over the next two weeks after describing previews of tonight's £27m opening ceremony as "spine-tingling".
David Cameron pledged Britain was ready to welcome the "greatest show on earth" after US presidential hopeful Mitt Romney cast doubt upon the country's readiness yesterday.
Jacques Rogge, president of the International Olympic Committee (IOC) added: "London is ready."
The Queen, who was following in the footsteps of her great-grandfather and father by opening the third London Olympiad, spoke earlier of the growing excitement as the torch went around the UK.
She told heads of state and VIPs at a reception: "To me the spirit of togetherness is a most important part of the Olympic ideal, and the British people can be proud of the part they have played in keeping the spirit alive.
"Many sports played in these Games have their historic roots in this country; and as a nation we have an abiding passion for sport, as well as a tradition of fair play and a good-natured sense of fun."
US First Lady Michelle Obama, who is leading the US presidential delegation which includes a ringside seat at tonight's ceremony, was also in east London to give her own personal good luck message to Team USA.
Mrs Obama urged America's athletes to "have fun, breathe a bit, but also win", as she met them at their training base.
Oscar-winning director Boyle said the curtain-raiser at the Olympic Stadium was fitting both for London and everyone who will compete at the Games.
Special effects, big names and bags of enthusiasm will be used to help celebrate the best of British in Stratford, east London.
Millions more globally are expected to tune in on television but many competitors will be missing from the long and late-starting athletes' parade.
Competition clashes or just preferring to rest instead as part of vital preparations mean that British swimmers, athletes, track cyclists and rowers will skip the ceremony.
Team GB has previously estimated about half of the 541-strong team will not attend, meaning major stars such as Jessica Ennis, Victoria Pendleton and Mo Farah may not parade at the climax of the big budget extravaganza.