The book Extreme Environments: Unique Ecosystems - Amazing Microbes is an attempt to showcase the uniqueness of extremophiles, the largely unexplored group that has the abilities to function in hostile conditions and represent the very ancient life forms that thrived on earth billions of years ago. The book covers a wide range of research achievements in the field of microbiology of extreme environments right from the conventional approaches of cultivation to recently evolved high throughput sequencing technologies. The book provides a broad spectrum of information about the taxonomy, physiology, ecology and biotechnological applications of extremophiles from various extreme environments across the globe.