The sun is rising over Capitol Hill and a day of great political theatre lies ahead.
America will celebrate the Inauguration with a momentary sense of national unity and pride. The crowds will line Pennsylvania Avenue and cheer Barack Obama - America's most improbable President since Abe Lincoln.
But come tomorrow morning, political combat will have resumed. This time the president will enjoy no honeymoon. Ferocious skirmishes will begin on the Budget, on raising the debt ceiling and on guns.
But by his own admission, President Obama is also bracing himself for something else: The Unknown.
He has called himself a student of the literature on presidential second terms. He knows that unexpected crises overseas or scandals at home can blow the White House off course. That happened to his immediate predecessor, George Bush Jr, and for both Bill Clinton and Ronald Reagan.
So as the president waves at the crowd - it is expected to be about a million strong - and then enjoys his lobster lunch on Capitol Hill, he will be hoping that the next four years allow him to concentrate on his own agenda.
But in the back of his mind he will be steeling himself for the event that every president has most feared since that fateful September day in 2001 - a terrorist attack on American soil.