If you close your left eye, what do you see? If you close your right eye, what do you see? If you don’t see anything, you forgot to open your left eye again!
The two images you saw were probably pretty similar. Your brain knows that and is able to put the two images together and make one single image.
With two eyes, we have a wider field of vision and can see more than we could with just one eye.
In a 3-D world, having two eyes helps us figure out how far away something is. Our eyes need to focus, or point themselves in certain ways, differently in order to see things at different distances. To see something very far away, our eyes can pretty much point straight forward. To see things really close, our eyes will have to slightly turn toward each other. The different focuses helps our brain figure out what is far away and what is really close!
Tricking Your Eyes
Stereograms are computer-generated images that trick your brain into seeing a 3-D shape on a flat image. It works because your eyes think the picture is not flat. Each of our eyes sees a slightly different image when we look at anything. The stereogram contains bits and pieces of slightly different images that trick our brain into automatically putting them together. When we focus in the right way, a 3-D image in the stereogram appears.
It may be tricky to see the images at first, but just focus on your focus! Staring at them too long might strain your eyes, so if your eyes feel sore, take a break.
Ask a grown-up to help you find some. A few links are in the Sources and Links section below.
Sources & links