Mansoulié here demonstrates his talent for communicating physics to non-scientists, his target audience for this brief, readable, volume." CHOICE The book comprises 15 short chapters, each presenting an important equation of Physics, from the simplest and oldest, to more complex and recent ones. The target audience is the interested general public, hence no mathematics is involved (beyond the simple expression of each equation). What can a professional "read" in an equation? Does one see a rainbow differently when one knows the law of refraction of light? Do some equations tell more than what they were invented for? The book presents an opportunity to think about the nature of the physical laws (without writing a philosophy treatise): are they written in advance, or only the result of our imagination? Memories and personal quotes in the book underline the intimate relation between a scientist and his research, and the interplay with his personal life. Each chapter is illustrated by a full page artistic drawing by Lison Bernet, sometimes kind, sometimes funny, and always poetic.