Bach, Johann Sebastian
Big Bang Theory
Khan, Hazrat Inayat
Khan, Pir Vilayat Inayat
Khan, Pir Zia
Pir o Murshid
As light enters the body through the eye it is focused onto the retina, the densest collection of sensory nerve cells in the body, averaging some 200,000 per millimeter. These cells include detail and color-oriented cones and motion and shape-detecting rods. Rods work together to detect even the littlest bit of light, while cones work individually, each responding best to a particular wavelength of light. These responses and detections travel through the optic nerve as electrical signals that the brain interprets as vision.
Not everyone sees in the same way. While some are color blind, and others can detect even infra-red light, most of us simply have our own set of colors to which we are most sensitive.
Of the light that strikes the human eye, 90% never reaches the retina. Much of it is reflected back into the environment, after being so close to discovery, and escapes, for the moment, unseen.
Image: Cross-section of the retina, showing its many layers.
Image source: Source: Image Gallery: Vision and the Eye.