An optical illusion is a visual phenomenon that tricks the eyes and brain into perceiving something that is not actually there or is different from what it appears to be. Optical illusions can take many forms, including geometric patterns, color illusions, and ambiguous images. They are often used in art and design as a way to create a sense of depth, movement, or illusionary effects. Optical illusions continue to fascinate and intrigue people today, and have inspired artists and scientists alike to explore the mysteries of perception and the human mind.