The eye, with its incredibly sensitive color vision, is increasingly being recognized as a marvel as we learn more about how it works. The eye is able to detect the smallest measure of light known to physicists. These units are called photons.
The normal human eye detects color, using principles similar to those used by our color television. Within the eye are three kinds of light absorbing molecules. They are found in the millions of cone shaped cells in the retina. Each one of these three molecules absorbs one of the primary colors – red, green or blue. How could "natural forces" have accidentally stumbled onto the very principal of physics upon which color rests?
The sensitivity required for color vision is also astounding. There is only 75 millionths of a meter difference between the wavelengths of blue and green light. This size difference is so small that it could not be noticed even under the most powerful light microscope. Yet, the eye has no trouble at all detecting the difference.
In his book On the Origin of Species, Darwin wrote, "To suppose that the eye, with all its inimitable contrivances for adjusting focus to different distances, for admitting different amounts of light and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest degree." On this one point we agree most certainly with Charles Darwin.