Stare directly into the dot at the center of the circle, your brain will decide to erase the circle itself showing only the white.
What: The Troxler fade, named after the discoverer Ignaz Paul Vital Troxler , was documented in 1804 in his paper named “On the disappearance of given objects from our visual field” (that’s an English translation, it was in German). You’ll notice, as you stare into the center and focus on it, the outer ring begins to fade, and then eventually disappears entirely… it will take moving your head or a hard blink to see it again.
How To: There’s not much to customizing this optical illusion, you can change the colors and thickness of the ring which will give you some idea as to how far you can push it.
Explain it: When you focus on an object the neurons that are used to process that information start to become fatigued and slow down, which leads to them slowing down and processing slower… eventually your brain begins to fill in the gaps as to what it’s seeing in between with the information it has, which in this case is largely a blank canvas… eventually the ring fades entirely and is patched up with the blank space.
I've researched these illusions in my spare time but am clearly not any kind of expert and my explainations are pretty smooth brained, if you find something mis-cited, earlier examples, or general mistakes please new let me know via firstname.lastname@example.org, be kind!