A stereogram is a picture within a picture.
Hidden inside each image is an object which appears in 3D when viewed correctly.
FREE pictures but also FREE softwares to create your own stereograms.

Optical Illusions can use color, light and patterns to create images that can be deceptive or misleading to our brains.
The information gathered by the eye is processed by the brain, creating a perception that in reality, does not match the true image.

Have fun with these amazing experiments & tricks !
Each one has an explanatory video.

Hundreds of FREE online games (require Flash Player here).
Please don't strain your eyes, take some regular breaks !! Use the 20-20-20 rule : every 20 minutes, take a 20-seconds break and focus your eyes on something at least 20 feet away.