A meteoroid that passes through the earth's atmosphere and falls to the ground. Also known as meteorites. The process of meteorite falling is a spectacular natural phenomenon. Meteorites come from outer space and have attracted people's interest since ancient times. These stones and iron blocks falling from the sky were recorded in Egyptian papyrus before 2000 BC. There are about 700 recorded meteorite landings in China, which is valuable information for studying ancient meteorites all over the world. In some countries with a long history in the world, some objects made of iron meteorites have been found in ancient tombs, which shows that ancient people have paid attention to the collection and utilization of meteorites. However, the real meteorite scientific research began after the practical application of testing technologies such as 1860 polarizing microscope. In recent 20 years, more than 5,000 meteorite specimens have been found and collected in meteorite shower, Allende, Mexico, meteorite shower, Jilin, China and Antarctica, which greatly promoted the study of meteorites. Besides moon samples and cosmic dust, meteorites are the main extraterrestrial materials that can be directly studied. Through the study and analysis of meteorites, a lot of cosmic information can be obtained.