Description:President Obama will already be serving his second term in office, when he takes the oath of office in front of thousands of people.
Up to 900,000 people are expected to watch the ceremony, in person, outside the U.S. Capitol building.
That’s about half the amount that filled the National Mall for the first one, four years ago.
President Obama was actually sworn into office on Sunday.
That’s because the U.S. Constitution says that the President must be sworn in by January 20-th.(3:31)