Water, a nonsubstitutional natural resource, is best described by Leonardo Da Vinci as 'the vehicle of nature' ('vetturale di natura'). This is the single most essential commodity responsible for the existence and sustenance of life on the planet earth. It is not at all an exaggeration to state that water is primarily responsible for the restoration of health, environment and prosperiy of human civilization. Unfortunately, this most precious natural resource is becoming increasingly scarce day by day. Water scarcity is among the main problems facing many societies around the world in the twenty-first century. Water use has been growing at more than twice the rate of population increase in the last century. According to a report from the United Nations, by 2025, 1800 million people will be living in countries or regions with absolute water scarcity, and two-thirds of the world's population could be under stress conditions. As emphasized in one of the UN's Millenium Development Goals (MDGs), water scarcity calls for strengthened international cooperation in the fields of technologies for enhanced water productivity. Recent years have witnessed impressive breakthroughs towards application of nanostructured materials such as carbon nanotubes (CNTs), metal/metal-oxide nanoparticles, zeolites, and dendrimers in the field of water purification. The present chapter aims to give an overview of the developments in the application of nanotechnology in water treatment, with a special emphasis on domestic water purification. The focus is oriented to the fact that the ultimate practical realization of this new technology is based on the assessment of the risks as well as benefits posed by nanostructured materials. The challenges involved in producing a well-defined integrated nano-based water purification device are discussed. © 2013 Woodhead Publishing Limited All rights reserved.