Its very name is confusing: "impossible shape." How can any shape be impossible? If someone draws a given shape, then it exists. And yes, it's true that impossible shapes can be drawn. They just can't be created in three dimensions.
Impossible shapes are a type of optical illusion. When we look at a drawing — a two-dimensional image — our brain automatically interprets the pictured item as a three-dimensional object as it tries to make sense of shapes and symbols. But impossible shapes are drawn with spatial inconsistencies that create depth that isn't there — or couldn't be there — in real life. Our brain fights to process drawings that are "incorrect," trying to turn them into something real and understandable. But it can't [sources: BrainDen, New World Encyclopedia].
Even more confused? You're not alone. Let's look at some impossible shapes and how you can draw one. That will help you better understand what they are and how they work.