The major objective of Materials Science is to encourage scientists and engineers to make informed choices regarding the design, selection and use of materials for specific applications. The materials scientist or engineer must:- Understand the properties associated with the various classes of materials.- Know why such properties exist and how they can be altered to make a material more suitable for a given application.- Be able to measure the important properties of materials and how they will impact performance.- Evaluate the economic considerations that ultimately govern most materials issues.- Consider the long-term effects on the environment of using a material. Materials scientists and engineers have developed a set of tools to characterize the structure of materials at various length scales, which can be examined and described at five different levels:1. atomic structure2. short- and long-range atomic arrangements3. nanostructure4. microstructure5. macrostructure.