North Korea's supreme leader Kim Jong-un presides over a country made up of five strictly hierarchical layers of social classes.
According to NKNews.org and based on a source who used to work for the North Korean police force, the five castes from the elite down are:
The system, known as songbun, was put in place by the founder of present-day Communist North Korea, Kim Il-sung (Kim Jong-un's grandfather), and is based on what happened during the 1950-1953 Korean War and the Japanese colonial period before that.
Your status is determined on the paternal side, and by how previous generations of your family acted during the war and occupation.
So the descendants of war heroes and generals would find themselves in the Special class. But deserters or people whose grandparents were subservient to the Japanese would be in the lower categories Complex and Hostile.
By 1967, the report says, the system completely determined where people were allowed to live, work, and what education their children received.
There are very few Specials, who form the elite of society, and it is thought that the Kim family are exempt from the class system altogether.
Nucleus, the second tier, is the largest caste. You have to be born as a Special or Nucleus - and lower than these classes there is severe and systemic discrimination.
Basics can work their way up into becoming Nuclei, but for Complex and Hostile citizens that is virtually impossible.
It's possible to raise your songbun either by hard work or by joining the Communist party as an official, and by being "awarded with an audience", or speaking with the Supreme Leader for more than 20 minutes (or taking a picture with him).
It was previously thought that there were only three social classes. The Complex classification was only added to the system in the 2000s and Special was also previously unknown.