santiago sierra's artwork, currently showing at Lisson Gallery in London, can safely be called revolutionary. Exhibits consisting of rectangular solid blocks neatly organized on the gallery floor may not draw attention until the viewer gets to know the material used to make them. The Spanish artist, known for challenging power structures, picked up human waste from New Delhi and Jaipur, and processed it for three years to produce his art (see pp 44-45). These blocks can also be used to make furniture, door panels and other utility products.

Far away from the London gallery in Bell Street, where connoisseurs contemplate these blocks in awe, more than two billion people in the world are in constant search for some place to relieve themselves everyday. Absence of toilets has taken a serious toll on the well-being of a majority of people in the low-income and developing world in the form of disease and social problems like high school drop-out rates among girls (see p 58). While the global bureaucrats say the Millenium Development Goal (mdg) for water is on track, achieving this for sanitation has turned out to be a Sisyphean task. Over the last decade, canny entrepreneurs have developed various business models for water. With believers in the