Picture of Optical Illusion - Black Squares and Gray Dots
In this optical illusion you will see gray dots at the intersections in the grid below. This is known as the Hermann-grid illusion. Those gray dots aren't really there. You can make them disappear by looking directly at the intersection.

In this Instructable we will go over a quick method for recreating such a grid and see some variations as well.
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Step 1: Starting the grid

Picture of Starting the grid
Get your favorite graphics program and we'll get started.

Start by making your basic building block: a black square with two identical smaller blue squares attached to the right side and bottom. The blue squares will determine the distance between the black squares.

Step 2: First copy

Picture of First copy
Grab the group of three squares, copy them and shift them to the right. This should give you what you see below. If you've mastered that step, the rest is a cakewalk.

Step 3: Keep copying

Picture of Keep copying
You can grab all of the squares, copy them, and shift them over. Do this twice and you'll have the first row of your grid.

Step 4: Second verse...

Picture of Second verse...
Apply the same technique you just used to create the row to create a series of rows.

Grab the whole row, copy it, and shift it down. Keep doing this until you have the grid you see below.

Step 5: Clean it up

Picture of Clean it up
Now select all the blue squares and delete them to get a nice clean grid of black squares. There are a few other ways of doing this, but for me this is the fastest.

Step 6: Play with variations

Picture of Play with variations
Try using different colors to see what happens and even inverse it so that there are white squares on a black field.

Have fun!