People try to make predictions about the future. But what surprises does technology have in store for us? The answer is nanotechnology （纳米技术）. 

Nanotechnology is the science of building tiny machines, so small that they are invisible. To give you an idea of the size of these machines, the difference between a nanometer and a meter two units of length, is the same as the difference between a rock and the planet Earth! Most scientists agree that nanotechnology will change our lives in the future—but how? At the moment it's difficult to predict whether this new technology will be like a wonderful dream, or a terrifying nightmare （噩梦）.

In the 1966 the film Fantastic Voyage, an inventor develops an amazing new way to treat diseases. He narrows a group of scientists and their machines and injects （注射） them all into a patient. They then travel around the patient's body, visiting the different parts of the body and repairing them. Of course, this is just a film—but the reality of nanotechnology is not very different. Scientists are already making nanobots, tiny robots that are very small. In the future, doctors might be able to inject these into a patient, and the nanobots will travel around the body and repair the diseased parts.

Some people are worried that nanotechnology could be difficult to control. Nanobots might come into the environment and damage people, plants and animals. Others have even more serious worries. Eric Drexler is a futurist, a scientist who makes predictions about the future. In his book Engines of Creation he predicted the invention of nanobots. He also described a special kind of nanobot that can make a copy of itself using the materials around it—and this is where the nightmare begins. In Michael Crichton's book Prey, nanobots reproduce themselves so quickly that they use all the materials around them and then look for more and more, and more, eventually "eating" the world. Some people are worried that this might really happen. The most serious predictions (that very few scientists believe) say that nanobots could destroy the whole planet in about three hours!