The first steps of vision take place in specialized cells in our eyes called photoreceptors. The pigment in these photoreceptors is called rhodopsin, which consists of the protein opsin and the chromophore retinal. When light hits rhodopsin it causes an isomerization reaction in retinal that changes the shape of the chromophore and of the entire protein, enabling the rhodopsin to interact with other proteins and initiating the visual signaling cascade that ultimately sends an electrical signal to the brain.