This figure is showing the steps in th evolution of the eye and the processes within those steps.  A) is depicting the molecular evolution within the eye, displaying transduction across the opsin and ion channel. Transductionr efers to transfering gewnetic material from one to the other, shown perfectly in the figure. B) shows the evolution of the cell structures themselves. The cell structure shown is composed of 4 main parts, rthe synaptic terminal, sxon, screening pigment and membrane stacking. C) shows the evolutionof cell types, shown this is a evolved cell possesing a pigment cell. There are two main cell tyes hwen it comes to eyes,  photorecptors & pigment, these cell type evolutions are thght to be from ancestral receptor cells (Nilsson, D.-E. (2009). D) is showing the eye as an organ shape evolution.  This picture shows where each part within the organ are found and how they are anatomically placed. 

Connecting it Together

As  mentioned previously in the page, rod and cone photorecptors play a huge role in vision, and how vison works. The rod and cone phtorecptors are similar, but difffernt  in their structure and function. Rods found in the outer retina, and sensitive to light thatsb how they developed to be best at dim/dark settings. Where cones found in the central retina, and thrive with quick wavelength reception and colored visual aid. The rods , Dichromatic vision were seen to have underwent mutation to create the Trichromatic vision. 

Further in the website, these two distinguishing types of vision in mammals will be dissected, but in order to understand it, its integral to have an understanding what the foundation of the distinguished eye is, the photoreceptor.