Have you seen Avatar? It's a popular 3D movie, and you may have to wear a special pair of glasses - 3D glasses, to see it. The 3D glasses make the images from the movie look as if they are coming straight at you. 3D movies are really exciting to watch. More and more 3D movies are coming to theaters. Some say that 3D TV sets will come into our homes in the near future. 3D technology can make TV and movies more exciting. However, people with eye problems may get headaches if they spend too much time watching 3D movies. Why? When we look at an object, each eye sees it at a different angle  . Our eyes send the two images to our brain, and the brain puts them together. 3D technology uses two film projectors  .  One projects left-eye-image and the other projects a right-eye-image. 3D glasses allow us to see a different image in each eye. So, when we are watching a 3D movie, our brain can't put together the images sent to our eyes. The brain needs to work harder at "reading" the images. That makes it easier for people with eye problems to get dizzy   or have headaches. Dr John Hagan, an eye doctor in Kansas City, said if your eyes can't focus on the same object at once, you will have trouble watching 3D movies. What is Avatar?
It's a kind of 3D projector. It's a kind of 3D TV set. It's a movie. It's an animal.