 Visual perception made simple. Our eyes are like windows to the world. We observe the smallest fluff on the rug and the farthest stars in the sky. At a stadium, we track the flight path of a soccer ball and perceive millions of different gradations of color. But how exactly does that work? The essential prerequisite is light. When it enters the eye, it first passes through the lens and the vitreous body before reaching the retina. There, it encounters millions of tiny photoreceptor cells with different jobs. Three types of cone cells, for instance, react to different wavelengths of light. That's why we can see a variety of colors. However, in order to do their job, the cones need enough light. At night, only the rods are active. They help us to perceive shades of gray and light-dark contrasts. That keeps us from walking into a lamp post in the dark. But all cats look gray at night. The rods and cones react to the energy of the incoming light and translate it into a language the brain understands — electric signals. Other cells down the line process these signals further. Some of those cells heighten light-dark contrasts. Others are in charge of sharpening the image. Nearly 130 million rods and cones are distributed between about one million nerve cells. And each of them transmits a different bit of information. That includes tasks related to shape, color, motion direction, and much more. The bundled tails of the nerve cells form the optic nerve. It's like a cable leading from the retina straight into the brain that transmits the signal almost instantaneously. Important for things like driving a car. Because we have two eyes, we also have two optic nerves. These cross paths and travel from the interbrain through a kind of substation straight into the visual cortex. In the visual cortex, the information from both eyes gets processed, filtered, interpreted, compared with existing patterns, and then reassembled into a complete picture. Other parts of the brain associate these elements with experiences and emotions. Anything missing is filled in. All of this usually happens unconsciously. However, important stimuli attract our attention. For example, if we recognize a familiar face in a crowd, we look more closely. And that irrelevant fluff on the rug, we ignore it. So actually we don't see with our eyes, we see with our brains. And through visual perception, each human being paints a unique mental picture.