A stereogram is a picture that looks like a lot of dots or lines until you look at it in a special way, and then you can see a 3D image.
Stereograms are fun and interesting because they hide a secret picture inside.
Examples:
The stereogram looks like a bunch of dots.
I can see a shark in the stereogram!
When I look at the stereogram, I see a bird.
I can't see the picture in the stereogram, it's too hard!
The stereogram has a dragon inside, but it's hard to see.
I love looking at stereograms and finding the hidden pictures.