Filter sterilization, that is, removing microorganisms by physical means such as screening or filter material adsorption, is a commonly used method of sterilization. The filtration method is widely used, and some materials that need to be sterilized cannot be heated, such as many vitamin solutions. In addition to being used in the production of beverages and drugs, the air is often sterilized by filtration. When we usually do microbiology experiments, the sterilized container is usually plugged with cotton at the outlet, which is actually filtering to remove microorganisms in the air, so that there is no microbial contamination in the air entering the container.