By Louisa Lim
BBC News, China
In one cafe in southern China, pictures of naked women hang on the walls - a rare sight in this country.
Even married couples are not necessarily sexually informed
But that is what this cafe is all about. It was set up by the City Government Reproductive Health Centre, and is an attempt to bring sex education into the open.
The centre's director, Tao Lin, showed me the services on offer - free condoms, and books and information about sex.
This drop-in sex education cafe is a pioneering concept, the first of its kind in China. Yet, it is almost completely empty.
Tao Lin admitted the hardest thing was breaking the taboo surrounding sex.
"Our challenge is that people are still too shy to talk about sex. It is difficult to know the right approach. People use tabloids or websites to find out information about sex, but it is often incorrect or unreliable," he said.
Out of sight
One survey has suggested that 75% of young Chinese learn about sex through pornography or porn websites, and computers certainly offer young people the chance to find out about sex in private.
In the back of the cafe, three young women are tapping away at keyboards.
"I want to find out about contraception, what choice there is, and how to use it," said 22-year-old pharmacology student Wu Dinliang, blushing.
She said she had never been taught about contraception.
Counsellor Tang Weiyao confirmed that even the most highly educated Chinese could be ignorant about sex.
"I had two university students who had been married for two years and hadn't managed to have children. They went to the hospital for a check-up and it emerged that they didn't even know the first thing about sex. They thought simply sleeping in the same bed would get her pregnant," she said.
For many other young people it is the opposite problem. They are exploring their sexuality without knowing how to protect themselves.
Lily Liu, from the British organisation, Marie Stopes, which has set up reproductive health centres in China, said one girl who came to one of the centres "was only about 19, and she had already had five abortions".
Many are embarrassed to visit sex education centres
But Ms Liu added: "Attitudes are becoming more open, and they are also having consensual behaviour [sic]. In fact, their knowledge is far behind what they should know.
"I think one of the reasons is that we don't have very good sexual education in schools. It is still very much centred around physiological development."
The organisation has developed radio shows to fill in the knowledge gaps. In one skit, two happy sperm race towards an egg. But the ad has a serious point, warning that having many sexual partners and not using condoms is unsafe sexual behaviour.
High levels of unprotected sex among young people are ringing alarm bells. Figures over the last few years show sky-rocketing rates of sexual transmitted infection [STI], according to Zhao Pengfei from the World Health Organization.
"We see, every year, 30 to 40% increases in the reported STI cases. Once HIV-Aids is introduced into that group it can be dangerous for the young generation," he said.
A recent survey has suggested that one fifth of people in China have never heard of Aids.
A question put to one radio agony uncle - "If I'm having lunch with an Aids carrier and I bite my tongue, can I catch Aids?" - is yet another warning sign that China's sex education system needs a revolution to keep pace with changes in sexual behaviour.
Otherwise, China will pay a high price for the ignorance of its youth.