The Chinese Communist Party's 73-million membership makes it the biggest political party in the world. Its tight organisation and ruthlessness help explain why it is also still in power.
The party oversees and influences many aspects of people's lives - what they learn at school and watch on TV, their jobs and housing, even the number of children they are allowed.
It is an elite group made up largely of government officials, army officers and model workers. Business people are also now being invited to join its ranks.
It is unrepresentative of China as a whole. Only 20% of members are women, 77% are over 35 years old and 31% have a college degree. It is also obsessive about control, regularly showing itself capable of great brutality in suppressing dissent or any challenge to its authority.
Joining the party brings significant privileges, which explains why membership continues to rise. Members get access to better information, their children get better schooling, and many jobs are only open to members.
Most significantly in China, where personal relationships are often more important than ability, members get to network with decision-makers influencing their careers, lives or businesses.
To join, applicants need the backing of existing members and to undergo exhaustive checks and examination by their local party branch. They then face a year's probation, again involving assessments and training.
The party has a pyramid structure resting on millions of local-level party organisations across the country and reaching all the way up to the highest decision-making bodies in Beijing.
In theory, the top of the pyramid is the National Party Congress, which is convened once every five years and brings together more than 2,000 delegates from party organisations across the country.
The congress' main function is to "elect" a central committee of about 200 full members and 150 lower-ranking or "alternate" members", though in fact almost all of these people are approved in advance.
In turn, the central committee's main job is to elect a new politburo and its smaller standing committee, where real decision-making powers lie.