The correct answer is: Pixel.
A pixel (short for picture element) is the smallest controllable element of a picture represented on a computer monitor or other display device. Each pixel is a tiny dot on the screen that can be turned on or off or made to emit different colors. The number of pixels in a picture determines its resolution, or how sharp and detailed it appears.
A silicon chip is a small piece of silicon that contains millions or billions of transistors. Transistors are tiny switches that can be turned on or off to represent data. Silicon chips are used in computers, cell phones, and other electronic devices.
An optical illusion is an image that tricks the brain into seeing something that is not actually there. Optical illusions can be caused by the way our brains process visual information, or by the way our eyes are designed.
An icon is a small image that represents a program, file, or folder on a computer. Icons are often used to make it easier to find and open programs and files.