Originated from studies on steam engines, thermodynamics is formulated traditi- ally for homogeneous materials. Applying to condensed matters however, laws of thermodynamics have to be evaluated with respect to the structural detail. Foll- ing after Kirkwood’s chemical thermodynamics, the author’s attempt is to discuss lattice dynamics in crystalline states in light of the traditional laws. It is noted that lattice symmetry remains as implicit in crystalline states if assumed as homo- neous, whereas deformed crystals with disrupted symmetry are not necessarily stable and inhomogeneous, exhibiting mesoscopic properties. In this context, the lattice dynamics in uniform crystalline states should accordingly be revised. Although mostly presumptive in the literature, such attempts should be formulated with fundamental principles for modern thermodynamics. I have selected structural changes and superconducting transitions for this book to discuss as basic pheno- na in crystals in thermal environment. Born and Huang have laid ground for thermodynamics of crystalline states in their book Dynamical Theory of Crystal Lattices. They assumed, however, that order– disorder phenomena were independent from the lattice dynamics, and hence excluded from their book. On the other hand, new evidence indicates that the problem must be treated otherwise; the lattice does play a vital role in ordering processes. Accordingly, I was motivated to write about physics of crystal lattice in the light of Born–Huang’s principles, which constitutes my primary objective in this book.