The United States honours and remembers its most famous civil rights leader today, as it marks Martin Luther King Day.
King, of course, was a Baptist preacher who fought against racism and discrimination in America in the 1950s and 60s.
Much of his struggle took place in the southern United States, where African Americans were essentially treated as "second class citizens" - facing widespread inequality, segregation, and at times, violence and police brutality.
King rose to prominence after he led a 385 day protest against segregation on the buses of Montgomery, Alabama.
Under the law, blacks had to sit at the back of the bus. And, if the bus was full, they had to give up their seats to white people.
During the campaign, King was arrested and his house was bombed. The campaign started on December 1, 1955, after Rosa Parks, an African American woman, was arrested for refusing to surrender her seat to a white person.
It ended on December 20, 1956, when a U.S. District Court ruling ended racial segregation on all Montgomery public buses.
In 1963, King helped organize the March on Washington, where he delivered his "I Have A Dream" speech.
If you've never seen it in its entirety, it is nothing short of remarkable.
In 1964, the U.S. Civil Rights Act made segregation illegal. That same year, King won the Nobel Peace Prize for his commitment to fighting racial inequality through non-violence.
In the mid 60s, he expanded his struggle beyond racism and segregation, to include poverty and the Vietnam War.
On April 4, 1968, King was assassinated in Memphis, Tennessee. He was 39.
A couple of seasons ago, Larry King was in the red chair and told a powerful story about Martin Luther King and Malcolm X. You can check it out below, starting at the 13:00 mark.
Dr. King was posthumously awarded the Presidential Medal of Freedom in 1977 and Congressional Gold Medal in 2004.
Martin Luther King Day became a U.S. federal holiday in 1986. And there is a monument in King's honour in Washington. Hundreds of streets in the U.S. also have been renamed in his honour.
During the civil rights movement, one of King's closest advisors was Andrew Young. He was in the red chair shortly after Barack Obama was elected for the first time.
It was an outstanding interview, with a passionate and eloquent man.
Today, one of the big events in Dr. King's honour is in Atlanta, where the King Center is hosting its annual commemorative service.
This year, the keynote speaker is Rev. Samuel Rodriguez - president of the National Hispanic Christian Leadership Conference. It's the first time a Latino leader has been the featured speaker for the service.
Today's holiday takes on added symbolism as it falls on the same day that President Barack Obama is being publicly sworn-in for his second term.
The public inauguration is taking place in Washington at the National Mall. Officials estimate as many as 800,000 people will attend today's ceremonies.
That's more people than actually live in Washington, D.C. It's also significantly fewer than the 1.8 million who were at Obama's first inauguration in 2009.
According to the U.S. Constitution, the date for inauguration is January 20. But because it fell on a Sunday this year, Obama was officially sworn in yesterday in a separate, private ceremony.
During today's ceremony, he will take the oath of office and deliver an inaugural address. That's followed by an inaugural parade down Pennsylvania Avenue toward the White House and a pair of inauguration balls this evening.
CNN has put together a neat little factoid called 'By The Numbers: Martin Luther King Jr. Day'. You can read it here.
U.S. News has republished an interview that 'U.S. News & World Report' did with King in February of 1964. It's entitled Martin Luther King, In His Own Words. You can read that here.
The New York Times has a post that includes a series of photos from the civil rights movement in the 60s. You can see that here.
And The Guardian also has a piece on the symbolism of MLK Day and Obama's second nauguration on the same day. Read it here.