Along the breathtaking Lhasa-Nyingchi Railway, a team of young bridge and tunnel engineers defies extreme conditions to maintain two of the world's most challenging railway structures: the record-breaking Zangmu Yarlung Zangbo Railway Bridge and the seismic-prone Bayu Tunnel. The Jiacha maintenance team consists of 13 young professionals from nine different provinces and autonomous regions across China, all born after 1990. They brave 40-story heights and four-hour drives to remote sites – just to ensure the Fuxing bullet train crosses safely in a mere 12 seconds.