Recently an increased amount of research work has been focused on negative refractive index mediums or Metamaterials. Hence, this book is aimed at presenting the possible applications of plasma as a medium for negative/positive refraction of electromagnetic waves. In the reference of composite metamaterials, this book brings models to achieve negative refraction using plasma. In another approach, study is conducted on hybrid plasma photonic crystal, which reveals that positive and negative refraction can be achieved by switching ON and OFF the plasma. Therefore, this book invokes the concept that plasma can be used to enhance the tunability/controllability of composite metamaterials and photonic crystals.