Histophysiology refers to the collective functioning of cells and tissues. In the case of the eye, these cells and tissues function in vision.

The human eye is sensitive to light having wavelengths between 397 and 723 nanometers (a nanometer is 10^-9 meters). The light entering the eye is focused by a lens to produce an image. The image is projected onto the back surface of the eye, a region called the retina. Here, specialized cells known as rods convert the light signal into an electrical signal. Chemically, this is accomplished by the bleaching out by the light of a rod protein called rhodopsin. Rods are important in lower-light vision, where color and detail are not as prominent. Color vision and the addition of visual detail is the concern of other specialized cells in the retina, which are known as cones. A trio...