The Pure Brightness Festival is the time when Chinese worship nature and heir ancestors. To worship ancestors is the centerpiece of the art works on the subject.
A society of natural farming economy employed slash-and-burn cultivation, burning mountains and destroying forest. Spring was a time when grass and trees start sprouting. To keep a balanced ecology and to preserve a better living environment was a necessity to 
human being's own survival. It was said in Li Ii -Yue Ling, "During this month, the air pressure of the sky comes down and the air pressure of earth rises up. When the sky and earth come together, grass and trees germinate. It is an edict from god to start farming." "It calls to respect mountains, forests, rivers and ponds, and to preserve female animals." To alert people not to cut trees, nor to kill female livestock in the time of spring propagation, no fire was allowed on the Pure Brightness Day. All cooked food had to be made the day before. On this day, every household had willow twigs on the door to welcome the arrival of spring. People also wore willow twig in their hair, and prepared lots of steamed bread or floury flower of "Cold swallow" to put on willow branches and jujube twigs to hang from the ceiling. It was a way to mimic the spring time on earth for the return of birds and swallows. A floury flower "Swallow plate" was a symbol of the universe, with a full fledged swallow and a bunch of young swallows perching on it.
