It's a huge day for America with less than an hour to go until Barack Obama makes history by officially becoming America's first black president.
Around two million people are cramming themselves into Washington DC to see for themselves the moment he takes the oath outside the Capitol Building.
When he's officially signed up as America's 44th president, it's time for a fresh wave of celebrations.
And they'll kick off with more than 90 groups taking part in a huge parade.
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Adam's latest report from Washington
During his inauguration ceremony, millions of people all over the world will be watching as Obama promises to preserve, protect and defend the US constitution to the best of his ability.
Then he'll make his first speech as president, which many are describing as one of the most eagerly awaited inaugural addresses in history.
To cope with all the people who want to be part of the Washington celebrations, a road which stretches nearly two miles from the Capitol to the Lincoln Memorial will be opened to the public for the first time.
And thousands of police officers are involved in one of the biggest security operations the state has ever seen.
Later in the day, it's party, party, party for the new president as he's expected to go to about 10 celebration balls across the city before heading back to his new home - the White House.
Loads of countries are joining in the fun by holding their own celebrations to honour him.
In the UK, events are being held in cities including Belfast, Edinburgh, Birmingham, Leeds, Liverpool and London.
Organisers say it's important for UK communities to mark Obama's success.