Broadly speaking, nano-materials refer to all kinds of solid ultrafine materials whose microstructures are modulated by nano-scale (1 nm- 100 nm) in at least one dimension, including zero-dimensional atomic clusters (the aggregation of dozens of atoms) and nanoparticles; One-dimensional modulated nano multilayer film; Two-dimensional modulated nanoparticle film (coating); And three-dimensional modulated nano-phase materials. Simply put, it refers to all kinds of materials composed of micron particles with nanometer grain size. The size of nanoparticles should not exceed 100 nm, but generally it should not exceed 100 nm. At present, ultrafine particles and their compact aggregates in the nano-scale range of 1- 100 nm, as well as materials composed of nano-crystallites, are collectively referred to as nano-materials, including metal, nonmetal, organic, inorganic and biological powder materials.

Nanomaterials can be divided into four categories according to their structures: zero-dimensional nanomaterials with atomic structure and atomic beam structure; One-dimensional nano-materials with fiber structure; Two-dimensional nanomaterials with layered structure; When the grain size in at least one direction is within a few nanometers, it is called three-dimensional nano-material. There are also various forms of composite materials mentioned above.