Sina Weibo, a Chinese version of Twitter, is one of the world's most popular social networking sites. And some of the stories it has generated give an interesting glimpse into life in modern China.

The impact of the internet on society in China is arguably greater than in any other country on earth.

Not only does it give people channels to express themselves - something which for political reasons has previously been almost impossible - but the increase of microblogging has amplified the internet's impact still further.

China's most popular microblogging service Sina Weibo - run by the country's largest internet portal, Sina.com - now boasts at least 300 million registered users, making it a serious challenger to Twitter.

Here we look at some examples of people whose lives have been changed by Weibo.

The dog rescuer

Zhang Xiaoqiu still remembers the date - 15 April 2011. It was when Weibo changed his life, and saved those of several hundred dogs. The Beijing-based businessman, originally from southern China, had always been an animal lover, but the news he heard via Weibo that day led him to take action.

Image caption Zhang Xiaoqiu helped rescue 300 dogs which were destined for dining tables in Chinese restaurants

Fellow internet users had spotted a truck on the motorway heading out of Beijing, loaded with dogs in tiny cages. This could only mean one thing - they were destined for restaurants in China's north-east, where dog-eating remains more common than in many other parts of the country.

Pictures of the caged animals, posted on Weibo, soon attracted the attention of hundreds of thousands of people across China, and at least 100 animal lovers quickly answered an appeal to jump in their cars and block the truck's path on the road.

Each time someone will send out a message on Weibo, and volunteers from all over the country will find out about it Zhang Xiaoqiu, Animal rights activist

Zhang was one of them. He and his wife arrived to find police and local government officials at the scene, and animal lovers attempting to persuade the truck driver to sell them the dogs.

Finally, after Xiaoqiu and other campaigners raised about £1,000 ($1,556), the driver agreed to drive the animals to the compound of the China Small Animals Protection Association (CSAPA) - the country's only officially recognised animal rights NGO.

Today, Zhang is a volunteer organiser for the CSAPA. He says there has been a dozen more dog rescues over the past year or so, all organised online via Weibo.

"Each time someone will send out a message on Weibo and volunteers from all over the country will find out about it.

"They start to phone the company transporting the dogs, phone the police, phone the animal protection society and the government. It puts enormous public pressure on these people, so they really have no choice but to take action."

Healing scars

In a cosmetic surgery hospital in Beijing, 17-year-old Zhou Yan lies motionless on her hospital bed, clearly still in pain from the scars and skin grafts on her face, arms and legs.

Image caption Zhou Yan received free treatment after pictures of her burn injuries were posted on Weibo

It is hard to imagine her life could be any worse but without Weibo, it might have been. One evening last September, the lively, intelligent teenager from the city of Hefei was attacked by a former classmate whose romantic advances she had rejected.

He threw lighter fuel over her and set her on fire, causing horrific burns.

At first her family kept quiet about what had happened, on condition that the attackers' parents paid the enormous cost of her treatment.

But when his parents stopped paying, and having received only limited help from the local government, the family decided to seek help online.

The pictures of Zhou Yan's injuries, which they posted on a popular web forum, went viral on Weibo. By the next day Yan's family had been overwhelmed with messages of sympathy and offers of legal and financial support.

Perhaps most significantly, the head of the Evercare cosmetic surgery hospital in Beijing contacted the family and offered Zhou Yan unlimited free treatment.

"I feel that the biggest help we've received is to know there's such a big spiritual support," says her mother Li Cong.

"If going online hadn't worked out, I was planning to take my daughter to Tiananmen Square in Beijing to beg for justice!"

And Zhou Yan says the online support changed her life.

"At first I felt that if I looked like this I was finished," she says, "but now there are so many people helping me… I'm quite confident about the future."

Although the family are still not satisfied with the 12-year sentence handed down to her attacker, they believe that without their online appeal he might have been released without charge - and they were at least able to make contact with the lawyers who are now helping them to bring a civil suit.

Cleaner air

Concern about China's environmental problems has been growing rapidly over the past decade, and Weibo has played a significant part in amplifying the voices of ordinary people on this issue.

Image caption Environmental campaigner Feng Yongfeng has used social media to campaign for clean air in Beijing

In October 2011, when Beijing's air quality became even worse than usual, it sparked a massive public debate on Weibo - particularly after celebrities, including real estate tycoon Pan Shiyi, began re-posting air monitoring data published by the US embassy in Beijing. This was information which the Chinese authorities had previously tried to block from reaching the public.

Eventually the Chinese government agreed, for the first time, to start publishing data from its monitoring of PM 2.5 - fine particles which are considered to be among the most hazardous pollutants.

"The public previously lacked a good channel to express their views," says Feng Yongfeng, an environmental activist and journalist who played a part in the campaign.

"But the internet and Weibo have brought a great change in how people can express their opinions - and the more people discussed this issue, the more powerful they became."

Yongfeng then launched an appeal on Weibo for donations to buy machines which would allow NGOs to monitor the air quality and check the government's figures - and several have already been purchased.

Recently he helped launch another online campaign to outlaw the use of shark fins in traditional Chinese soup.

"Weibo will bring society changes which cannot be stopped," he says. "It's not just a tool for passing on news, it's also a means of taking action.

"The technology creates a direct and equal link from person to person [and] this spirit really fits with the idea of civil society - you can spark lots of campaigns via Weibo, and inspire lots of people to get involved."

China's counter-culture

In an old factory in Chengdu, 21-year-old Gas is hard at work. But with his baggy jeans, baseball jacket and bohemian beard he hardly looks like the traditional Chinese worker.

Image caption Authorities regularly wipe the work of Chinese graffiti artist Gas but it lives on via his online gallery

Gas is, in his own words, a "graffiti writer", an artist who spray-paints his tag, based on the Chinese character qi - meaning "air" or "the energy in the body" - on walls around Chengdu and his nearby home town.

Being a graffiti artist can be a lonely business in China. Until the past few years, graffiti was almost never seen here, and even now Gas estimates there may only be a few thousand serious aficionados in the country.

The police and local authorities regularly scrub away his artwork soon after the pieces are finished, but now he uses Weibo to post the images he paints direct to over 1,000 followers in China and Hong Kong - and it has also helped him become friends with other graffiti artists around the country.

"It's like another kind of travelling," he says. "I don't have to travel myself, but my works can travel via the internet."

It is an example of how the internet, and Weibo, have contributed to the rapid growth in alternative culture - from hip-hop to vegetarianism - among a young generation eager to express themselves in this fast-changing nation.

Mumsnet, China style

The formation of online mothers' groups has been a particular feature of the internet in China over the past decade, as women who were previously isolated have taken to the web to share information about pregnancy and parenting.

Image caption Parenting groups have sprung up all over China thanks to social media activism

Weibo has helped bring these groups closer together - in real life as well as in the virtual universe of the internet. In an airy play centre in a modern office building in the western city of Chengdu, mothers-to-be meet regularly at weekends to discuss the benefits of breastfeeding.

There is a lot of pressure in China, including from doctors, for women to feed their babies formula rather than breast-milk.

Organiser Yushi got involved in the group when it was just a forum with a handful of members on an older social networking platform - now it has more than 5,000 followers, and more than 200 women have attended its meetings.

Yushi has now launched a social enterprise to promote breastfeeding in hospitals in Chengdu, and is also starting a campaign to reduce the dependence on Caesarean sections for childbirth in China.

"Without the internet I don't know if I would be able to do this work," she says. "If there is no internet I might have been forced by the doctors to have a C-section and I might use formula too, because I see all the benefits in the ads on TV."

Now she hopes their campaign will spread:

"I think if you change the mother then society will change, that's why we are doing this. We use the internet to let more mothers know what's good and let them decide by themselves."

Duncan Hewitt is a writer for Newsweek magazine and lives in Shanghai. He presents It Started with a Tweet for the BBC World Service.

Listen via the World Service website or download the podcast.