14. Why Phase Diagram is important in engineering? It is important to the engineer relates to the design and control of crystal structure. It important to the engineer relates to the design and control of heat-treating procedures. It important to the engineer relates to the change and amend of material atomic structure. It important to the engineer relates to the change solid and liquid phases. 15. What is "Microstructure"? * Microstructure is structure includes proton, neutron and electron. Microstructure is atomic structure. Microstructure is material's crystal structure. Microstructure are defects, impurities, grains, and grain boundary