Kim Jong Un was born on January 8 — 1982, 1983, or 1984.
His parents were future North Korean dictator Kim Jong Il and his consort, Ko Young Hee. He had an older brother named Kim Jong Chul and would later have a younger sister named Kim Yo Jong.
While Jong Un's official birth year is 1982, various reports suggest that the year was changed for symbolic reasons, including that it was 70 years after the birth of Kim Il Sung and 40 years after the birth of Jong Il.
Jong Un — here with his mother — lived at home as a child.
During this period, North Korea was ruled by "Great Leader" Kim Il Sung. While Jong Il was the heir apparent, Jong Un's path to command was far less certain.
Then it was off to Switzerland to attend boarding school.
Called "Pak Un" and described as the son of an employee of the North Korean embassy, Jong Un is thought to have attended an English-language international school in Gümligen near Bern.
Jong Un is described by former classmates as a quiet student who spent most of his time at home, but he had a sense of humor, too.
"He was funny," former classmate Marco Imhof told The Mirror. "Always good for a laugh."
"He had a sense of humour; got on well with everyone, even those pupils who came from countries that were enemies of North Korea," another former classmate told the German newspaper Welt am Sonntag. "Politics was a taboo subject at school ... we would argue about football, not politics."
Jong Un loved basketball and idolized Michael Jordan.
The young Korean reportedly had posters of Jordan all over his walls during his Swiss school days. Although Jong Un was overweight and only 5-6, he was a decent basketball player.
"He was a fiercely competitive player, very explosive," former classmate Nikola Kovacevic told The Mirror. "He was the play maker. He made things happen."
"He hated to lose. Winning was very important," said former classmate Marco Imhof.
He also had a "fantastic" collection of Nike sneakers.
After school in Switzerland, he returned home for military schooling.
Upon his return to North Korea, Jong Un attended Kim Il Sung Military University with his older brother. Some reports say they started to attend their father's military field inspections around 2007.
While his father faced death, Jong Un was rapidly promoted up the chain of political and military leadership, despite having little experience in either.
He was made a four-star general, deputy chairman of the Central Military Commission of the Workers' Party, and a member of the Central Committee, according to the BBC.
Jong Un has a theme song known as "Footsteps."
"Footsteps" looks and sounds like a propaganda song from the Soviet Union.
The song calls people to follow in "Our Admiral Kim's footsteps." Here's a sampling of the lyrics:
Footsteps, Footsteps ... spreading out further the sound of a brilliant future ahead ... tramp, tramp, tramp, ah, footsteps.
Many North Koreans see Jong Un as a youthful version of "Great Leader" Kim Il Sung.
Kim bears a clear resemblance to his grandfather, Kim Il Sung, in appearance, haircut, and mannerisms.
Rumors had circulated that Kim Jong Un had received plastic surgery to enhance the resemblance even further, although the North finally responded and called the allegations "sordid hackwork by rubbish media."
"The false report ... released by enemies is a hideous criminal act which the party, state, army and people can never tolerate," said the official Korean Central News Agency.
After his father died, Jong Un was quickly declared "Supreme Leader" of North Korea.
When Jong Il died of a heart attack on December 17, 2011, the young Jong Un inherited the world's fourth-largest military, a nuclear arsenal, and absolute control over North Korea.
He took over ahead of his older brother Jong Chol, who their father thought was "effeminate" and weak. His other brother Jong Nam apparently said negative things about the regime, according to The Australian.
Around 30 when he took power, Jong Un is the youngest head of state in the world.
Some originally believed that Jong Un's aunt and uncle were actually calling the shots.
Among Jong Un's most trusted advisers were his aunt Kim Kyong Hui and her husband, Jang Sung Taek, both 66. The couple was reportedly ordered by Jong Il to control the country's military and help the young leader consolidate his position while he gains more experience.
At a recent meeting of the DPRK Workers' Party, both were photographed sitting close by. Their most important job, it seems, is to push his role as a powerful figure among some generals who do not trust him, according to The Telegraph.
But at the end of December 2013, Jong Un had his uncle and his uncle's family executed, apparently in a bid to stop a coup against his rule.
On December 12, 2013, Kim Jong Un had his uncle Sung Taek executed. He was charged with having tried to take control of North Korea through a military coup. Following the uncle's execution, there were reports that Jong Un continued to purge the rest of the uncle's family.
But North Korea's ambassador to the UK denied that Sung Taek's family was also executed. Instead, the ambassador claimed that only Sung Taek was killed by firing squad following a trial.
He's married to a former cheerleader and may have two kids.
Leaders in the hermit kingdom are often very secretive when it comes to their significant others, but Jong Un often has his wife join him and allows photographs.
North Korean media revealed in July that he was married to Ri Sol Ju — a former cheerleader and singer — but no one knows exactly when they were married, according to NBC News.
South Korean intelligence believe the couple probably married in 2009 and already had one child. There are rumors Sol Ju gave birth to a child in 2012, with many believing it was a girl.
The couple is believed to have had another child, in 2015.
Jong Un lived out a childhood fantasy when former Chicago Bulls star Dennis Rodman visited.
Everyone in the family is apparently a huge Chicago Bulls fans.
His father owned a video library of "practically every game Michael Jordan played for the Chicago Bulls."Jong Il tried unsuccessfully to get Jordan to visit in 2001.
Jong Un had tons of Jordan posters as a kid. Brother Jong Chol was photographed as a child wearing a Bulls Jersey: No. 91 — Rodman.
But recently, things haven't been going so well.
In 2013 he was reportedly the target of an assassination attempt. South Korean intelligence believes the young leader was targeted by "disgruntled people inside the North" after he demoted a four-star general, which resulted in a power struggle.
Perhaps as a means of reasserting control, Jong Un has become extremely belligerent, shutting down all links with South Korea and threatening thermonuclear war against his neighbor and the US. His father and grandfather used to make these threats all the time without following through.
Jong Un has continued to be belligerent with South Korea and the West throughout his rule in hopes of bolstering his authority.
North Korea has continued to test ballistic missiles and nuclear devices under Jong Un's rule, despite the threat of sanctions. In 2012, the country launched its first satellite into space. And since Jong Un has taken over, the country has continued to push ahead with its construction of ballistic and nuclear weapons.
In 2013, North Korea conducted its third-ever nuclear test and its first under Jong Un. And in April 2015, a top US general warned that North Korea could develop nuclear missiles capable of reaching the shores of the western US.
Jong Un's belligerence reached a peak in 2016.
On January 5, North Korea conducted its fourth-ever nuclear test and its second under Jong Un. Pyongyang claims the test was a miniaturized hydrogen bomb.
In response to the detonation, world leaders have strongly come out against North Korea. Even China, North Korea's main ally, has said that it strongly opposes the tests.
In response to the bomb, the UN is planning further sanctions against North Korea.