For the past 50 years, the world has grown used to crazy threats from North Korea that don't lead anywhere.

But the threats have taken a decidedly sharper and more ominous tone under Kim Jong-un, the third Supreme Leader of the country.

On Wednesday, North Korea claimed to have successfully detonated a miniaturised hydrogen bomb.

Here is how Kim Jong-un grew to be one of the world's most concerning world leaders.

Kim Jong-un was born on January 8 — 1982, 1983, or 1984

The exact year in which the head of state was born is not known STR/AFP/Getty Images (STR/AFP/Getty Images)

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 Kim'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 Kim Jong-il.

Kim 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, Kim'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, Kim is thought to have attended an English-language international school in Gümligen near Bern.

Kim is described by former classmates as a quiet student who spent most of his time at home, but he had a sense of humour, too.

"He was funny," former classmate Marco Imhof told the Daily 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."

Kim loved basketball and idolised Michael Jordan

The young Korean reportedly had posters of Jordan all over his walls during his Swiss school days. Although Kim 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 Daily 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

The leader quickly progressed in political and military leadership Reuters (REUTERS)

Upon his return to North Korea, Kim 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, Kim 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.

Kim 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 sample of the lyrics:

Footsteps, Footsteps ... spreading out further the sound of a brilliant future ahead ... tramp, tramp, tramp, ah, footsteps.

Many North Koreans see Kim 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.

Rumours 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, Kim was quickly declared 'Supreme Leader' of North Korea

When Jong Il died of a heart attack on December 17, 2011, the young Kim 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, Kim is the youngest head of state in the world.

Some originally believed that Kim's aunt and uncle were actually calling the shots

Among Kim'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 gained more experience.

At a 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 Daily Telegraph.

But at the end of December 2013, Kim 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 Jang 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 Kim continued to purge the rest of his uncle's family.

But North Korea's ambassador to the UK denied Jang's family was also executed. Instead, the ambassador claimed that only Jang 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 Kim 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 rumours 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

The athlete made his first visit to the country in 2013 Reuters (Reuters/Thomas Peter)

Everyone in the family is apparently a huge Chicago Bulls fan.

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.

Kim had tons of Jordan posters as a kid. Brother Jong-chol was photographed as a child wearing a Bulls jersey: Number 91 — Rodman.

But recently, things haven't been going so well

In 2013 Kim 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, Kim has become extremely belligerent, shutting down all links with South Korea and threatening thermonuclear war against his neighbour and the US. His father and grandfather used to make these threats all the time without following through.

Kim 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 Kim's rule, despite the threat of sanctions. In 2012, the country launched its first satellite into space. And since Kim 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 Kim. 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.

Kim's belligerence reached a peak in 2016

On January 5, North Korea conducted its fourth-ever nuclear test and its second under Kim. Pyongyang claims the test was a miniaturised 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.

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