"Because of their lengthy experience telling, organizing and digging into the stories of these people, the guides at memorial halls often tell warm and touching stories about them," says Chen.

Scholars present a more comprehensive, systematic understanding of the person and their contributions, and were sources of reliable information.

To ensure accuracy, the first draft of each episode was written by a scholar. Then, the directors revised the draft to make it more suitable for a documentary. For example, the episodes on Cai were the work of Chen Hongjie, who has written a biography about him.

"If our directors had jumped into the sea of literature, they might not have been able to find the most important events in the educators' lives and work, the most significant decisions they made, or the stories that typify the value of their ideas. So we invited professional researchers to build frameworks for us," Chen Hong says, adding that due to limited length of episodes, a large amount of material gathered could not be used in the series, and will be published in book form in the future.

Sun Xiufeng, director of the episodes about Ma, says he was impressed by how one of his students, an 88-year-old professor at Tsinghua University by the name of Wu Wenhu, was eager to be interviewed about his former teacher.

"He said that many people he knew his age didn't enjoy such good health as he did, and that he still took part in cultural and physical activities organized by the community. He owes all this to his habit of exercising, formed as a Tsinghua student under the guidance of Ma. He even choked up when he recalled details," says Sun.

Artificial intelligence technology was used in the production. In one episode about Cai, deepfake imagery based on photos and a video was used to make a lifelike re-creation of a scene of Cai managing teachers at Peking University in 1917.

"I believe there's enormous room to create with the help of AI that is still waiting to be explored. AI tools will become better and more varied, enhancing the beauty and influence of documentaries," Chen Hong says.

Contact the writer at wangru1@chinadaily.com.cn