This chapter provides an explanation of what leads to the emergent properties of water and how these properties provide conditions for living organisms to thrive. At one time, it was thought that living things could be found only where a moderate range of abiotic factors (such as temperature & pH) existed. Since the discovery of extremophiles, micro-organisms that thrive in extreme environments, our understanding of where life can exist has changed. Some extremophiles live in hot, acidic sulfur springs and some even live near the openings of deep ocean hydrothermal vents. What does the existence of life in such environments say about the possibility of life on other planets?