How were optical illusions made?

Optical illusions are created by manipulating visual perception through various techniques, such as contrast, color, shape, and perspective. Artists and designers often use specific patterns and arrangements to trick the brain into seeing something different from reality. Techniques like ambiguous images, impossible shapes, and motion effects exploit the way our eyes and brain process visual information, leading to surprising interpretations. These illusions rely on our brain's interpretation of visual cues and can reveal the complexities of human perception.