PHOTO: The result of presidential stress

What do Barack Obama, Bill Clinton, George W. Bush and Ronald Reagan have in common besides holding the highest office in the United States? Their hair turned gray during their presidencies.

VIDEO: Obama's celebrate at ball

After celebrating his second inauguration with a throng estimated at about 800,000, President Barack Obama and first lady Michelle Obama spent the evening at more intimate affairs: 30,000 guests at two inaugural balls.

Obama embarks on first day of 2nd term

Four years ago, President Barack Obama and his staff spent the first day in the White House learning the basics. But plenty of fresh challenges lie ahead.

Complete text: Obama's inaugural address

Obama got a loud cheer Monday in his inaugural address when he said the nation's journey remained incomplete "until our wives, our mothers, and daughters can earn a living equal to their efforts."

VIDEO: Beyonce performs national anthem

Singer Beyonce had the honor of performing the national anthem at the closing of President Obama's second inauguration on Monday, January 20, 2013 in Washington, DC.

VIDEO: Did Obama flub during oath?

President Barack Obama stumbled slightly during his swearing-in today.

Inauguration 2013 schedule of events

President calls for equality in address

Obama got a loud cheer Monday in his inaugural address when he said the nation's journey remained incomplete "until our wives, our mothers, and daughters can earn a living equal to their efforts." WATCH ENTIRE SPEECH VIDEO INSIDE

Obama, Biden take oath of office

President Barack Obama took his ceremonial oath of office today at the U.S. Capitol before an enormous crowd on the National Mall.

PHOTOS: Inauguration celebrations

Click inside for photos from the second inaugural celebrations for President Barack Obama .

Obamas start inauguration day at church

President Barack Obama and his family are beginning inauguration day by attending services at St. John's Episcopal Church near the White House.

Inauguration firsts

Take a look at the history of "firsts" during Presidential inaugurations.

Inauguration Bibles

Here is a look at the history of Presidents and Bibles used during inaugurations.