If you stare for 1 min at this photo it will disappear. It relates to how intelligent is your brain.
It is an optical illusion called the "Troxler fading," Troxler is a scientist published a scientific paper under the title of "On the disappearance of given objects from our visual field," 200 years ago.
the explanation is that your brain is very good at adapting to the surrounding environment. For ex. if you wear tight pants. at first, you will feel it but with time this feel will disappear. that is the same mechanism here, when you stare at any point of this photo. your brain will focus on this point and forget the remainning parts of the photo.
More info: reddit.com
