For a long time, antennas have been widely adopted for signal transmission and receiving in applications where electromagnetic (EM) waves are involved. These include radar, TV and radio broadcasting, satellite communications, point to point communications, and current wireless communications. Design techniques have been developed to produce antennas with different properties that fulfill the requirements in these different applications. Recently, new types of fabricated structures or composite materials that mimic media with non-natural EM properties were introduced in the microwave and optics fields. These new types of materials are known as metamaterials. With the flexibility and new properties provided by metamaterials, new type of antennas has been conceived, while making their designs more straightforward.