In 1998, Zhang moved to Shenzhen, a city that represents China's reform, and also a place where lots of migrant workers lived. He captured migrant workers lining up at the train stations to grab tickets to go home, and the "spider men" who helped clean high buildings and their scarred, gnarled hands, testament to their hard work and toil.

Zhang's works are regarded by critics as a comprehensive and fascinating portrait of migrant workers.

At the exhibition, there's a photo that has changed the destiny of many children who couldn't afford to go to school in the 1990s. It's Xie Hailong's photo of a girl with big eyes, writing in her notebook in a run-down classroom.

A newspaper photographer at the time, Xie went to a rural village in Anhui province. He walked into a primary school and happened to see a girl in shabby clothes studying hard in a classroom where the brick walls were full of holes.

After the photo was published, it evoked an incredible response and many people began donating money to support children like the girl in Xie's photo. From then on, Xie went to 128 poor villages in more than 20 provinces and took tens of thousands of photos to show children in need of help.

"There are photographers who often find stories behind the surface. Their works reflect another side of the world. But sometimes, they just photograph the people and things they are familiar with. It's a shared memory," says the curator.