Three dimensional (3D) metamaterials are artificial micro-structures periodically arranged in three-dimen-sional space. The lattice constant of metamaterial is much smaller than the wavelength of the incident EM wave, so the metamaterial can be treated as an artificial effective medium for the propagating of the EM waves. By controlling the geometrical parameters of its lattice, the metamaterials can be developed with properties never found in nature, which can be utilized to manipulate the propagation of EM waves, such as blocking, absorbing, capturing, or bending waves. With these magic properties, 3D metamaterials get bright prospects for applications in stealth technology, communication technology, optical imaging and sensing technology.