Guides in China's provincial pavilions have mastered the art of the perfect smile to greet visitors. Photos by Xinhua

"A smile can bring us closer to each other. At the end of the day, I find my cheeks ache because I have been smiling for so long," Nie said, adding that her legs also hurt at the end of each day from standing.

"We have to stand at least eight hours every day. It is really a painful task, especially during the first few days I worked here."

Nie said this was the first time she has had to stand for such long periods.

"We have 30-minute break time after standing one hour. But the time always passes so quickly."

As Miss Chongqing, Nie is always the center of attention.

"Every day there are thousands of visitors taking pictures with us. Perhaps years later, when those visitors take out the photos of their Expo trip, they will say: 'Hey, look! This pretty girl is from Chongqing, China.' And our wonderful city will once again be remembered," she said.

"Many visitors like to pose with me for a picture and some asked my name and want my mobile phone number," she said. At first, the young women gave out her number, but she soon learned to politely refuse.

"After all, our appearance represents our hometown. I hope I can bring the best side of Chongqing to the world."

Nie said she is optimistic about her work. "I don't let the pressure get me down and just keep smiling."

Pretty pavilion girls form much of the scenery at the Expo Garden. At the Heilongjiang Pavilion, visitors will meet more beauty.

" Every visitor who comes into our pavilion praises our girls for their beauty," said Li Deshan, director of the Heilongjiang Pavilion. "They are the pride of Heilongjiang."

The girls in Heilongjiang Pavilion were chosen after rounds of rigorous selection. And they work hard, putting in 10 hours a day at the pavilion.

Heilongjiang Pavilion receives about 20,000 visitors every day, which means a lot of work for the staff.

"The work here is hard. But we're happy that people always praised us for our charm and beauty," said Bing Lin, a guide in the pavilion and student at the Harbin Civil Aviation School.

Wearing a navy blue uniform and make-up, it is difficult to guess she is only 15 years old - the youngest among the girls in Heilongjiang Pavilion.

"I'm very glad I got the job, but the work is much tougher than I thought it would be," she said.

"There are many visitors wanting to check out the Heilongjiang Pavilion and it is usually a long wait to get inside. "Some impatient visitors get angry with us," Bing said. "But we always patiently explain the situation to them.

"But we represent the image of Heilongjiang, so all these hassles can be forgotten," she said.

Zhai Zhaokun, another pretty guide at the Heilongjiang Pavilion, said: "What impressed me most is that many Shanghai people with memories of my province visit the Heilongjiang Pavilion."

During the Cultural Revolution (1966-76), many "educated urban youth" were sent to work in the countryside.

"They spent the prime of their lives in Heilongjiang and have fond feelings for the area. They said Heilongjiang was their second home," Zhai said. "Hearing their words, I feel very proud that I was born in the place."

Before the start of Expo 2010 Shanghai, nearly 300 attractive young women, most of them college students, were selected from over 10,000 contestants in a nationwide competition. More than 30 million people voted for the winners over the Internet.

The winners, who became Expo guides, had two months intensive training in etiquette and deportment, among other things.

"Through the comprehensive training course, these young women are better prepared in knowledge, etiquette and ability. This helps them properly and fully represent China," said Sun Weimin, an official with the Shanghai World Expo Coordination Bureau.

"The unique features of the local environment always give special characteristics to its inhabitants. And women from different areas will undoubtedly have unique cultural and environment backgrounds," said Chen Jun, a visitor from Shaanxi province, who is also an amateur photographer.

Chen said he has taken many photos at the Expo Garden, especially of pretty ladies from different provinces, who are guides in the various pavilions.

"Behind every woman's smiling face there is a different cultural story. It also reflects different features from across the country," he said.

Nie Aixin was crowned Miss Chongqing last month.