One country, two systems
| It doesn't stop|
at the water's edge
One country, two systems (一國兩制) is a Chinese political and economic system proposed by Deng Xiaoping in the 1980s to get Hong Kong and Macau back from Britain and Portugal, both former imperial states.
This meant that Hong Kong and Macau were officially Chinese territory, but they would guarantee at least 50 years of strong self-rule in politics, economy and society, which in principle is similar to before the handover to China.
In the late 1990s, Britain and Portugal gave their final colonies, Hong Kong and Macau respectively, to China. However, as both had been influenced by their colonial masters, the powers both made agreements saying that the two cities would have home rule for at least 50 years. This means that China will be able to revoke the home rule from the cities in 2047 for Hong Kong and 2049 for Macau. Since both have developed their own distinct ways of life, it is unknown how it will play out, but it probably won't end well if China tries to reduce or end the autonomy, as both are effectively city-states.
While the one country, two systems principle was well adhered to between 1997 and 2000, when Hong Kong was first returned to China, the 2010s saw a backlash from many liberal Hong Kong citizens as the Communist Party of China tried to intervene actively in Hong Kong's politics. This corresponded with General Secretary of the Communist Party of China Xi Jinping's consolidation of power within mainland China. It hasn't yet been 50 years yet, but the one country, two systems principle is increasingly being undermined.