Metamaterials are artificial materials engineered to provide properties which "may not be readily available in nature". These materials usually gain their properties from structure rather than composition, using the inclusion of small inhomogeneities to enact effective macroscopic behaviour. This book reviews research in the field of metamaterials including the application of optical metamaterials in ultrasensitive detection of chemical or biological species; the patch antenna and the perfect absorber with dendritic cell metamaterials; metamaterials as the cloaking device for obtaining electromagnetic invisibility; the results of electromagnetic field analyses in different types of metamaterials performed by using full-wave simulations and others.