When traveling to mountains and forests in autumn, you can always see red and yellow leaves all over the mountains, with layers of forests dyed, like a colorful picture scroll. Many people are attracted by this beauty, but they do not know the popular science principle behind it. The reason why autumn mountains and forests change color lies in the change of pigments in the leaves. Leaves contain four main pigments: chlorophyll, lutein, carotene, and anthocyanin. The content of these pigments changes in different seasons. In summer, chlorophyll content is the highest, making the leaves green. Chlorophyll helps leaves carry out photosynthesis and produce nutrients; in autumn, as the temperature drops and light decreases, chlorophyll gradually decomposes and its content decreases, and lutein, carotene, and anthocyanin, which were originally covered by chlorophyll, gradually appear. Lutein and carotene are yellow and orange, which is why many leaves turn yellow in autumn; anthocyanin is red and purple. The lower the temperature and the stronger the light, the higher the anthocyanin content, and the leaves will turn bright red, such as maple leaves and Cotinus coggygria. Different tree species have different pigment contents and different color change times. For example, maple trees usually change color in mid-October, and ginkgo trees in late October, which is why the autumn mountains and forests are rich in color. Understanding these popular science knowledge, when traveling to autumn mountains and forests, you can clearly understand the origin of this beauty and better appreciate and feel the natural beauty.