Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online.Photonic metamaterials are a type of electromagnetic metamaterial. These are designed to interact with optical frequencies (mid-infrared). As a type of EM metamaterial, the periodic structures are made up of single units called cells. These single units are much smaller than the wavelength of the radiated source. In the case of photonic metamaterials, the radiated source is at optical wavelengths. Furthermore, the sub-wavelength period disttnguishes the photonic metamaterial from photonic band gap structures. This is because the special optical properties do not arise from photonic bandgaps, but rather from an interaction with light which mimics atoms or ions. However, the periodic cells (meta-atoms) are fabricated on a scale, which is much larger, magnitudes larger, than the atom.