Contractor Shen, the chief of his team, does the check-up work. Photos by Li Ning and Zhu Yu

Beijing Film Academy (BFA) student Li Ning made a sudden detour on his way to class, veering his car from the northern Fourth Ring Road and towards the steel framework of the "Bird's Nest".

Li's companion and classmate, Zhu Yu, was hardly surprised by his impulse. After all, the emerging National Stadium lying on the capital's central axis had dominated both their lives for more than a year.

Bracing against a biting wind on this frigid winter's day, the pair of young filmmakers left their car and trudged toward the site, eager to catch up with the migrant workers they had come to know over these past months. "It may turn out to be a novel angle for filming if it's a rainy day," Li muses.

Li and Zhu, both third-year students at BFA's Photography College, have spent countless hours documenting construction of the Bird's Nest from vantage points such as the bridge located a few hundred meters away. From spring to winter last year, the pair appraised light and trained their viewfinder, capturing the human journeys behind the mammoth Olympic building project. They call these migrant workers "Nest raisers".

The students' initiative took seed in April 2006, with a large-scale photography contest, "Olympic Tower Raisers", organized by the Beijing Photographers' Association.

"We both jumped in and for the first time, got so close to the construction site of the stadium," says 22-year-old Zhu. "It really astonished me when it jumped into my eyes, and I was aware that an unusual experience had just begun."

Li Ning and Zhu Yu, students at Beijing Film Academy's Photography College, have spent one year documenting construction of the Bird's Nest. [China Daily]

"But in retrospect, our pictures were superficial. We were like visitors on a cursory sightseeing trip, picking up snaps instead of getting to the heart of subject."

Afterward, a different idea popped into Zhu's mind. She decided to track some of the builders at the Bird's Nest. Zhu wanted to experience their living conditions, and shoot an original and vivid documentary.

"We want to focus on migrant workers who are the supporting part of this tough project, and film one section of the history of their lives in there," 21-year-old Li says.

With the support of their parents, they soon owned the necessary photographic equipment and became regular callers at the stadium. They filmed the builders at work, and also went on excursions with the three central characters of their documentary, to record their leisure time at locations such as Tian'anmen Square or Qian Men.

The documentary follows three migrant workers from Liyang, Jiangsu Province, a town known throughout the country for its steel and boiler production - known to the filmmakers as contractor Shen, welder Li Anming and electrician, old Di - gradually became better acquainted with the two visitors, and were willing to vent their feelings.

"This was of vital importance for the documentary," Li says.