How far away is the invisibility cloak from us? Conceptual diagram of invisibility materials by Zhou Yun, Zhan Qiankun, and Zhao Chunfu. From the invisibility helmet of the hero Perseus in ancient Greek mythology, to the use of invisibility by Sun Wukong in Journey to the West to participate in a peach banquet in the Yaochi Lake, behind these wonderful fantasies in literary works are human imagination and longing for the unknown. With the development of science and technology, the invisibility skills in mythological stories are gradually entering reality. Not long ago, at a scientific event, Chu Junhao, an academician of the CAS Member, introduced the "effect test of various optical stealth methods", and demonstrated the "stealth" realized by using "mysterious materials" on the spot, which was amazing. This is a special material that can refract light in a regular manner. When light passes through this material, the object behind the material is "compressed" into thin strips. When there are enough lenses, the object will be decomposed into countless identical thin strips. Since the human eye cannot distinguish these thin strips, the object looks as if it has disappeared. What is the uniqueness of this "mysterious material"? What other stealth materials are there in the field of stealth? What are the future application prospects of these stealth materials? Today, let's explore the truth. Starting from the disappearance of the lower body, how many people in this world would fantasize about how magical it would be if they could become invisible. And now, this fantasy is accelerating into reality. Imagine, with just a transparent panel and a gentle turn in front of you, a part of your body immediately disappears without a trace. Chu Junhao, an academician of the CAS Member, successfully hid his lower body with such materials. In fact, "lower body disappearance technique" is not magic, but the power of optics. As is well known, vision is the most important way for humans to obtain information, with over 70% of information transmitted through visual nerves, and in the process of transmission, light is indispensable. Light propagates along a straight line, and once the propagation mode of light is artificially changed, such as curved propagation, the implementation of invisibility becomes possible. It is reported that the material used to help Academician Chu Junhao achieve the "invisibility" effect is a cylindrical mirror grating. This kind of "mysterious material" is like a magic mirror. When an object stands in front of it, something magical happens: the mirror will bend the light, making people unaware of the existence of the object. It is like a magic mirror in the movie Harry Potter, giving people the power of invisibility. Column mirror grating is actually a high-tech optical material. Its magic lies in its resemblance to a magical transparent crystal ball, with each piece neatly arranged by many tiny cylindrical convex lenses. These convex lenses are like a group of mysterious magicians, able to make light dance gracefully in a waltz according to a specific rhythm and melody. When light passes through these convex lenses, it feels like magic has been cast, compressing them into thin lines. As the number of lenses increases, these lights seem to be split into beams of light, piercing through the objects behind them. When your gaze falls on it, it's like passing through a busy knitting machine, and all you see is a dense array of light, while the object behind the convex lens seems to have disappeared from this world. Chu Junhao