"I also contacted a postgraduate student from Yale University's history department to work with her. It was a good cooperation experience that has also made us learn a lot," she adds.

With a touch of regret, according to director Chen Lei, the documentary could have featured more countries, but their previous plans to film the growth of millet in northern Namibia and yams in Papua New Guinea had to be canceled because of COVID-19.

Aside from the overseas stories, the crew also delved into some of the most far-flung areas of rural China, interviewing locals to trace how their centuries-old agricultural traditions have been preserved.

For instance, they traveled to a scarcely populated village on the border of Shanxi province and the Inner Mongolia autonomous region and managed to convince an elderly couple who farm hulless oats to share their decadeslong dedication to the land.

Analyzing the in-depth meaning of the documentary, Chen Xiaoqing says that the team members believe that the diversity of grains has shaped human activities, and helped civilizations emerge in different areas.

"Each grain was once the source of energy for the people of a land and the foundation of a civilization," Deng says. "And the fate of grain is highly related to the historical fate of humankind. We hope everyone can have more knowledge of different kinds of grain, sort of as a way to protect and preserve the diversity of cultures."