This book addresses various aspects of physics, using Quantum oscillation (QO) as a common denominator. QO plays an important role in many aspects of physics, such as the Weinberg angle, Caribbo angle, neutrino oscillation, K
0
oscillation and CP violation, mass generation by the Higgs field, hadron mass pattern, lepton anomalous magnetic moment, spin precession, hydrogen HI line, etc. Usually, these subjects are taught separately. As such, this book allows readers to learn about a wide range of physics subjects in a unified manner and to gain farther-reaching perspectives. The readers may be surprised at the fact that different looking physics are actually closely related with each other. They will also find essential information on quantum mechanics at the heart from many concrete examples. Though the book is mainly intended for graduate students of particle, nuclear and astrophysics, undergraduate students and researchers will also benefitfrom the content.