The position of the Earth when a certain solar term is used, as well as its climate features, are considered the elements of "heaven", while those of "Earth" are represented by animal activities, plant growth and farming.

The roles of "man" are represented by regional customs and folk festival celebrations, related ancient poems, as well as diet.

The principle is also seen in the design of the book covers, with patterns showing the sun's orbit, typical plants of the seasons and representative human activities.

Chen says that the solar terms represent the Chinese people's respect for nature and expectations of a good harvest.

"It is the natural laws that are behind the folk customs," Chen says, adding that the environmentally-friendly theme reflected in Chinese solar terms is consistent with the spirit of the current times.

Meanwhile, Chen wants to change the impression of traditional Chinese culture being monotonous and relatively hard to understand.

Yu Zhenyue, the illustrator of the picture books, says that the internet era provides more opportunities for cartoonists to create works with their painting skills, animation techniques and narration.

According to Chen, it took the team working on the books more than a year to complete the project, and he added that it is also working on a TV anime series on the 24 solar terms.