In his 2003 speech at Rice University’s Energy & Nanotechnology Conference, the late Nobel Laureate Richard Smalley highlighted the 10 problems for the next 50 years. In his list, sits at the top, and water comes next. Now, with the price of solar power , the dawn of a new energy is just around the corner. As a result, is going to be the greatest challenge for humanity. But the water problem is . First, unlike coal and oil, water can not be . Second, water is with every other sector of society. Third, while water demands are growing, climate change is intensifying droughts and floods and water supplies are . There are solutions, such as building water-transfer aqueducts, hydroelectric dams, and desalination plants. But they may be incredibly . It will for scientists to find affordable solutions to the water problem. Before that, everyone should do his or her bit to water.