What will power your house in the future? Nuclear, wind, or solar power? According to scientists at the Massachusetts Institute of Technology (MIT) in the US, it might be leaves -- but artificial   ones. Natural leaves are able to change sunlight and water into energy. It is known as photosynthesis  . Now researchers have found a way to imitate this seemingly simple process. The artificial leaf developed by Daniel Nocera and his colleagues at MIT can be seen as a special silicon chip with catalysts  . Similar to natural leaves, it can split water into hydrogen and oxygen when put into a bucket of water. The hydrogen and oxygen gases are then stored in a fuel cell, which uses those two materials to produce electricity, located either on top of a house or beside the house. Though the leaf is only about the shape of a poker card, scientists claimed that it is promising to be an inexpensive source of electricity in developing countries. "One can imagine villages in India and Africa not long from now purchasing an affordable basic power system based on this technology," said Nocera at a conference of the American Chemical Society. The artificial leaf is not a new idea. The first artificial leaf was invented in 1997 but was too expensive and unstable for practical use. The new leaf, by contrast, is made of cheap materials, easy to use and highly stable. In laboratory studies, Nocera showed that an artificial leaf prototype   could operate continuously for at least 45 hours without a drop in activity. The wonderful improvements come from Nocera's recent discovery of several powerful, new and inexpensive catalysts. These catalysts make the energy transformation inside the leaf more efficient with water and sunlight. Right now, the new leaf is about 10 times more efficient at carrying out photosynthesis than a natural one. Besides, the device can run in whatever water is available; that is, it doesn't need pure water. This is important for some countries that don't have access to pure water. With the goal to "make each home its own power station" and "give energy to the poor",  scientists believe that the new technology could be widely used in developing countries,  especially in India and rural China. The main idea of this passage is about   _  .
saving energy a mixture of water power and solar energy an invention copying photosynthesis an introduction to the history of artificial leaves