The "One Country, Two Systems" principle was an idea that first came into existence in the 1970s.
In the early 1980s, Deng Xiaoping put forward the concept in an effort to realize the peaceful reunification of China.
According to Deng, there is only one China - under this premise the Chinese mainland adheres to the socialist system while Hong Kong, Macao and Taiwan may retain their capitalist systems.
A new Constitution of the People's Republic of China was endorsed relating to the concept on December 4, 1982.
"One Country, Two Systems" was only a basic principle and policy until the enactment of Hong Kong's mini constitution, the Basic Law.
That document was drafted in 1985 and approved by China's top legislature, the National People's Congress, five years later. The basic principles and policies were translated into a national law with a general binding effect, forming the basis for the administration of Hong Kong.
The Chinese national flag and the flag of the Hong Kong SAR fly at Golden Bauhinia Square in Hong Kong. /VCG Photo
The Chinese national flag and the flag of the Hong Kong SAR fly at Golden Bauhinia Square in Hong Kong. /VCG Photo
The "One Country, Two Systems" principle has been adhered to in Hong Kong for twenty years now.
Andrew Fung, director of the Hong Kong Policy Research Institute, says that although there are still many challenges in the future, the principle has been largely successful.
"We are facing many political challenges because of some radicals trying to advocate the independence for Hong Kong," he said.
Pro-independence activists claim Hong Kong doesn't have democracy or freedom of speech. Fung says that those statements are wrong.
"According to the freedom index by the Heritage Foundation in the past several years, Hong Kong is running the freest society in the whole world, so freedom of speech is here in Hong Kong," he emphasized.
Hong Kong also enjoys a degree of democracy. According to Fung, Hong Kong has universal suffrage for half of the seats on the Legislative Council.
"We are Chinese and the Hong Kong residents are Chinese nationals under ‘One Country, Two Systems’, so that we should move forward together for mutual benefits to contribute further for the development of China," he said.