The term “materials science and engineering” emerged in the 1960s to represent how the engineering application of materials was increasingly based on scientific principles, rather than the empiricism typically used prior to World War II. Materials science focuses on understanding how the properties (or characteristics) of materials are based on their atomic- and microscopic-scale structure. The term microstructure refers to this microscopic-scale structure. Materials science grew out of the fields of physical chemistry, polymer chemistry, and condensed-matter physics.