This optical illusion is a variation on the previous optical illusion with the gray ghosts appearing in the intersections of the black grid.
We still have a black grid here, but now the lines are gray and there are white circles in the intersections. Have a look and try to count all of the black dots you see.
Step 1: What black dots?
The black dots you see don't really exist. Whenever you try and look at one directly, it will disappear. I don't know why this happens as I haven't found a good explanation for it. Feel free to let me know if you have any insight into the comments.
The goal of this Instructable is to show you how to quickly recreate such a grid with a graphics program. You can then make some variations of your own.
To start with we'll want a gray background. Lock this or put it on another layer and then start making your building block.