Earth - soil - is the oldest and most widely used building material in the world today. For at least 9,000 years, people have mixed dirt with water to make adobe to build their homes. Today adobe and several variations on this earth-based building technique are experiencing a new popularity. These "green" building methods are becoming economically competitive with standard construction methods. Other features like long-term energy savings, ease and speed of construction, and the knowledge that by building "green" you're doing less harm to the environment make these construction alternatives even more attractive.