This book discusses the extremophiles explored for biosynthesis of nanoparticles. Nanotechnology is a widely emerging field involving interdisciplinary subjects such as biology, physics, chemistry and medicine. A wide variety of microorganisms, such as bacteria, fungi and algae are employed as biological agents for the synthesis of nanoparticles. Novel routes by which extremophiles can be employed to generate nanoparticles have yet to be discovered. The book is divided into 5 major chapters: (1) Major types of nanoparticles in nanotechnology (2) Diversity of microbes in the synthesis of nanoparticles (3) Extremophiles in nanoparticle biosynthesis (4) Applications of nanoparticles produced by extremophiles (5) Challenges and Future perspectives.