Engineered material have found many applications in all ranges of frequencies, because new electromagnetic properties can be achieved using these structures. Considering trasnmission of EM wave through a planar 2D periodic structure, some resonances can be seen in the transmitted signal. These resonaces have very low quality factor (Q), because the resonating elements in the structure are strongly coupled to the radiation into the free space. It has been shown that by introducing some small asymmetry in the structure, high Q resonances can be achieved. These sharp asymmetric resonances are called Fano resonances.