When photographer Hei Ming looks at pictures taken in front of the Tian'anmen Rostrum in the 1960s and now, one thing in particular strikes him. Photos taken during the "cultural revolution" (1966-76) often show people holding small books of quotations from former Chairman Mao Zedong, a daily necessity at that time.
But when Hei invited them to take new pictures with the same poses, they substituted Mao's book with senior citizens' cards, mobile phones, bank passbooks or passports.
"The unanimous ideology of Chairman Mao's book, which was almost a must in the past, has given way to various items like the mobile phone. It is obvious that Chinese people's thoughts and ways of living have become more diverse," Hei says.
Hei, 45, is well known for his documentary photography series such as 100 monks and 100 educated youths. Technically, See You Again, Tian'anmen, is perhaps the simplest of all of his works, yet he regards the project as one of the most important in his career.
He says the project gave him a chance to break through the limit of a certain group of people and to capture the changes of the country over the past 60 years.
The project began five years ago, when Hei began to collect ordinary people's pictures taken before the Tian'anmen Rostrum, which is located in the heart of Beijing and long recognized as the political symbol of China.
Having collected more than 500 such pictures, taken at various time from the 1940s to the 1980s, he tried to find those people in the pictures and asked them to come back to Tian'anmen and take new pictures.
He has taken more than 200 pictures so far, of people standing in the same position and at the same time of a day, and with the same pose.
"Tian'anmen is basically the most popular backdrop for Chinese people to take pictures. When you compare the new pictures with the old, you can see the changes in Chinese people and society in the last six decades, in a microscopic yet vivid way," he says.
For most people who traveled to Beijing in the 1970s, a photo at Tian'anmen was among the most important things to do.
"It was a great honor to have a picture taken with the backdrop of Tian'anmen. For us living in remote Xinjiang, the honor came with hardships," says Duan Li, a woman in her early 50s.
When Duan, her sister and parents arrived in Beijing in 1972, they had spent seven days on a bus and train journey from their home in Altay, Xinjiang Uygur autonomous region. The first thing they did after checking into a small guesthouse was to go to Tian'anmen and take a picture together.
"There was a long queue. We registered and paid the fee before we had the photo taken, and we wrote down our address on an envelope for them to mail the photo. The photographer was standing on a high wooden platform. The camera was fixed, and everybody was standing in fixed positions, with the same postures and expressions," she recalls.
A month later, they received the photo. To share it with relatives, they mailed the negative to Shanghai to develop more copies. Besides sending copies to others, they had one enlarged and colored to keep as a family treasure.
When Duan learned about Hei's project from the newspaper 37 years later, she and her sister decided to join up, though their parents had passed away. Again they came to Beijing from Xinjiang, but this time it only took them 4 hours to fly from their home in Urumqi.
"We found the place where we stood with our parents. We tried to pose the same way as we did in our teens, only to find that we could no longer squat as easily as we could. Our parents, who stood behind us, will never be with us again. We could only recall our parents and our youth by taking a picture at Tian'anmen," Duan says.
The oldest picture that Hei has collected was taken on Sept 30, 1949, the day before the founding ceremony of the People's Republic of China. The three persons in the picture were photographers with North China Pictorial, who photographed the founding ceremony.
This May, 85-year-old Yang Zhenya, one of the three people in the picture, stood before Hei's lens at Tian'anmen for a new photo. His two colleagues passed away in the 1990s.
"When the three of us took the picture in 1949, I didn't realize that it would become a historical photo," says Yang. "How time flies, both Tian'anmen and me have changed a lot."
In a picture taken in 1966, four "red guards" gathered around a portrait of Mao in Tian'anmen, all in armbands, smiling and holding books of Mao's quotations.
When Hei took a new version of that picture in 2007, however, only one person remained in the picture. Zheng Panqi, now 60, held a book of Mao's works and squatted alone before Tian'anmen. The four young men came from various areas in Beijing full of "revolutionary" spirit. They met in Tian'anmen Square, and took a photo together as a memento. Then they went their own ways and lost contact.
Zheng, who was a middle school student at that time, was a soldier and a college student in the years that followed, and is now a professor with Tianjin Professional College of Art and Design.
"This picture depicts an exciting moment in my life. For the first time, I was at Tian'anmen, and I felt that I was with Chairman Mao," he says.
Today, Tian'anmen is still a popular spot for photos, but people no longer have to condense all their emotions in a picture as before.
"In the past, any one who left or came to Beijing would have to take a photo at Tian'anmen," said 54-year-old Yang Lang, vice-president of the SEEC Media Group. "People seem to have exalted the political meaning of Tian'anmen. Today I drive past Tian'anmen every day, but no longer have that kind of feeling."
Hei has already finished shooting, and is now working on the text for each group of photos. He hopes to release a book and hold an exhibition of all the photos in September, before the 60th anniversary of the founding of the People's Republic of China.
"I hope to present history through the details of the common people," he says.