At the atomic level it is the electronic configuration of the atoms that is of interest. At the mesoscsopic length scale, the atomic organization into crystalline or amorphous (or glass-like) structures and the presence of defects in these structures is the governing issue. 

At the microscopic length scale, the single crystalline, polycrystalline, or non-crystalline nature of the material will influence the response of the macroscopic material. 

At the macroscopic length scale the form of the material, such as rod or tubular sections, and their combination into a system will be the focal issue.