Night vision refers to the people's ability to see in the darkness. Scientists found that human being can only see a very small percentage of all the light, which is called visible light. In order for people to see what's going on at night, mainly for military purpose in he beginning, scientists started the long journey of research for night vision.

Scientists found two factors are impacting people's night vision, the spectrum of light and the light intensity, which means that people can have good night vision either the spectrum is within people's visual range, or the light intensity is intense enough for people to recognize the objects in front.

Many animals like cats have much better night vision. Anatomy of these animals' eyes shows they have larger eyeballs, bigger lenses and bigger pupils. Scientists speculated that some animals' night vision equals to generation 1 or 2 night vision devices.

The simplest way to improve people's nightvision is the way driver's night vision eye glasses work. Night vision eye glasses for driving purpose use peculiar lenses to expand the spectral range of light and people's nightvision can be improved by being able to see different shades and contrast of light.

While most of the nightvision devices are pretty high-tech instruments. These nightvision devices are image intensifiers amplifying the dim or weak light to the visible signals for human beings, which range from active infrared generation 0 to passive generation 3. These nightvision devices were developed for the military purpose but now are also widely used in civilian spheres.