You might not like to think so but it's amazing how easily your brain can be manipulated. Either tricked into believing it's seeing something that isn't there or unable to distinguish two images from one another, it's always a thrill to have your brain mangled temporarily. Part trick and part exploitation of how the brain process sensory information, optical illusions are a great way to alter the way you see and perceive information. That goes someway to explaining what the ''Magic Eye'' craze that swept the globe during the 90's. Anyone not familiar with the Magic Eye phenomenon (there is an example below for your convenience), it involved staring at a multicoloured poster for what seemed like an eternity and you might see an image appear before your eyes. It never worked for the majority but that didn't stop people from putting up Magic Eye posters everywhere. Thankfully you are about to see much better examples of optical illusions and ones that will leave you scratching your head. So click next and prepare to have your brain completely melted by 21 mind boggling optical illusions.