The Müller-Lyer Illusion is a visual phenomenon where two lines of equal length appear to be different lengths due to the presence of arrow-like figures at their ends. One line has arrows pointing outward, while the other has arrows pointing inward. This creates an optical illusion that tricks the brain into perceiving one line as longer than the other. This illusion highlights how our perception can be influenced by surrounding visual cues. It demonstrates the brain's reliance on context and shape to interpret size, revealing the complexities of human vision and the way we process visual information.