Many Microorganisms and some macro-organisms can live under extreme conditions. For example, high and low temperature, acidic and alkaline conditions, high salt areas, high pressure, toxic compounds, high level of ionizing radiation, anoxia and absence of light, etc. Many organisms inhabit environments characterized by more than one form of stress (Polyextremophiles). Among them are those who live in hypersaline and alkaline, hot and acidic, cold/hot and high hydrostatic pressure, etc. Polyextremophiles found in desert regions have to copy with intense UV irradiation and desiccation, high as well as low temperatures, and low availability of water and nutrients. This book provides novel results of application to polyextremophiles research ranging from nanotechnology to synthetic biology to the origin of life and beyond.