Optical illusions are illusions that rely on the way our brains work to completely fool us. We may think we see the world exactly as it is, but the truth is our brains, more often than not, complete images for us, show us details that don't exist and even change the color of what we're looking at so it can make more sense. Born with ancient brains, our minds still belong to cavemen, so it is of little surprise how well they can fool us. This quiz will test your ability to understand these optical illusions. Ready to try?