By Michael Bristow
BBC News, Beijing
Zeng Jinyan does not look like a dissident. She is small, heavily pregnant and has a liking for colourful dresses.
But the Chinese security operatives who permanently watch the apartment she shares with her husband are an indicator of just how influential she has become.
The 24-year-old uses the internet to pass on information to the outside world about protests, injustices and underground campaigns in China.
She is just one of tens of thousands of ordinary Chinese people who are now using the internet to express themselves in ways that were previously impossible.
Ms Zeng, who is due to give birth next month, has been detailing her daily life on a blog for several years.
She came to prominence when her husband, Hu Jia, was arrested in 2005.
Mr Hu, also a rights campaigner, was detained by police for 41 days - although at the time his wife did not know where he was.
As word of her blog spread, other people started contacting Ms Zeng to tell her about their own stories, which she then retold on the internet.
"I want people to know that not only me, and not only my husband, face such a situation," she says.
"Actually, in China many people are under house arrest or are illegally detained or are under surveillance for the whole year."
Her activities - predictably - attracted the attention of China's security services.
Ms Zeng's blog is now blocked in China and secret police keep constant watch outside her suburban Beijing home.
Her internet connection is often cut, but she keeps sending out e-mails and updating her blog for those abroad who can still access it.
The campaigner is not the only Chinese person using the internet to express themselves.
Those using the internet in China cut across the social divide, and use it for a variety of reasons.
Some internet jokers have dared to poke fun at President Hu Jintao
Internet chatrooms are important gathering places, where people can express themselves more openly, even if it is just to share jokes.
And political humour directed at those in power - almost impossible to find in the state-run Chinese media - exists on the internet.
Recently, a photograph of a river crab with three wrist watches on its pincers and body was passed around by internet users.
In Chinese the phrase "river crab" sounds like harmony, a watchword of current Chinese President Hu Jintao. A crab can also be taken as a symbol of bullying.
And in Chinese the words for three watches can be rearranged to sound like "the three represents" - a political theory developed by former Chinese President Jiang Zemin.
Some internet users suggest the symbol should be used as the mascot for the Chinese Communist Party's 17th congress.
Ahead of the congress - China's most important public, political event - some party officials used the web to publicise their hopes for the gathering.
The internet is also being used as a tool to organise.
When prices went up at a university canteen recently, in the southern city of Guangzhou, hard-up students decided to stage a boycott.
Word of the boycott was apparently spread using online messaging services, with reports that two-thirds of students joined the protest.
And parents who believe their missing children have been kidnapped to work as virtual slaves in brick kilns use the internet to drum up support for their case.
Of course, the Chinese authorities try to crackdown on what they see as subversive material on the internet, as elsewhere.
Unwelcome foreign websites are blocked in China, censors edit news sites and ordinary users have to show their ID cards to enter a web cafe.
But the internet is hard to police and, with few other avenues for open debate available to ordinary people, its influence is set to grow.
This article is part of a week of special coverage on how China is ruled.