||From the analysis of the spectra of black-body radiation¡BX-Ray¡BHydrogen atom and photoelectric effect, the concept of quantization is introduced and the duality of matter and wave is also introduced. Combining the idea of quantization and the semi-classical hydrogen model of Bohr, the structure of atom is described. Solving the Schrodinger equation, the deduced wave function is related to the probability of finding the electron in space, a particle in the potential well and in a box. The concept of atom is expanded to the molecular and the energy band theory of solid state physics. The energy band theory deduced from the modern physics is applied to account the optical, electrical and thermal properties of solid states, wherefore the fundamental principles and the applications of electro-ceramics are introduced.