This book presents the most comprehensive and methodical work on the theory of the moire phenomenon, providing a full general-purpose and application-independent exposition of this fascinating effect. Based on the Fourier theory, it leads the reader through the various phenomena which occur in the superposition of repetitive layers, both in the image and in the spectral domains. The first chapters of the book present the basic theory, covering the superposition of monochrome, periodic layers. In later chapters the theory is extended to the even more interesting cases of polychromatic moires and moires between repetitive, non-periodic layers.Throughout the whole text, the book favours a pictorial, intuitive approach which is supported by mathematics, and the discussion is accompanied by a large number of figures and illustrative examples, some of which are visually attractive and even spectacular. This book is intended for students, scientists, engineers and any readers who wish to widen their knowledge of the moire effect. It also offers a beautiful demonstration of the Fourier theory and its relationship with other fields of mathematics and science. The prerequisite mathematical background is limited to an elementary familiarity with the Fourier theory.