Theoretical Models for Photonic Crystals -- to Part I -- Models for Infinite Crystals -- Models for Finite Crystals -- Quasi-Crystals and Archimedean Tilings -- Specific Features of Metallic Structures -- Optical Properties of Photonic Crystals -- to Part II. The Many ‘Facets’ of Photonic Crystals -- Control of Electromagnetic Waves -- Refractive Properties -- Confinement of Light in Zero-Dimensional Microcavities -- Frequency Conversion -- Fabrication, Characterisation and Applications of Photonic Band Gap Structure -- to Part III -- Planar Integrated Optics -- Microsources -- Photonic Crystal Fibres -- Three-Dimensional Structures in Optics -- Microwave and Terahertz Antennas and Circuits -- Conclusion and Perspectives.Just like the periodical crystalline potential in solid-state crystals determines their properties for the conduction of electrons, the periodical structuring of photonic crystals leads to envisioning the possibility of achieving a control of the photon flux in dielectric and metallic materials. The use of photonic crystals as a cage for storing, filtering or guiding light at the wavelength scale thus paves the way to the realisation of optical and optoelectronic devices with ultimate properties and dimensions. This should contribute toward meeting the demands for a greater miniaturisation that the processing of an ever increasing number of data requires. Photonic Crystals intends at providing students and researchers from different fields with the theoretical background needed for modelling photonic crystals and their optical properties, while at the same time presenting the large variety of devices, from optics to microwaves, where photonic crystals have found applications. As such, it aims at building bridges between optics, electromagnetism and solid-state physics. This book was written by six specialists of nanophotonics, and was coordinated by Jean-Michel Lourtioz, head of the Institut d'Électronique Fondamentale in Orsay and coordinator of the French Research Network in Nanophotonics.