Microcapsules generally refer to hollow micron-sized microspheres. Because the middle is hollow, the drug loading is large, which is similar to our common capsules, but the particle size is micron. Generally, microspheres refer to micron-sized solid microspheres, that is, solid spheres. The microspheres mixed with drugs and wall materials have a good protective effect on drugs, such as sodium alginate microspheres and chitosan microspheres. Nanoparticles are solid particles with an average particle size below 500 nm, and strictly speaking, they must be below 100 nm. There are many kinds of nanoparticles. The sodium alginate and chitosan mentioned just now can be made into nanoparticles through ionic crosslinking, as well as self-assembled block polymers and amphiphilic macromolecules. These materials can be self-assembled into nanoparticles by ultrasonic in water phase. Meanwhile, some metals such as gold and silver. Liposomes are tiny vesicles wrapped in lipid bilayers. Generally, natural lipids such as cholesterol are used as wall materials, and the particle size is 50-2500nm. Therefore, the differences among microcapsules, microspheres, nanoparticles and liposomes are mainly 1 and average particle size; 2. Whether the sphere is hollow or solid; 3. Wall materials.