Optical illusions are like little tricks your brain plays on you, and they never fail to leave you scratching your head. Some illusions make a still image look like it’s moving, while others have you questioning whether two lines are really the same length. There are those famous ones, like the dress that was blue and black or white and gold, and they literally divided the internet. Then there’s the illusion where a flat drawing suddenly looks 3D—your brain just fills in the gaps! These mind-twisters aren’t just fun; they also teach scientists how our brains process visual information.