Chromophore

The pigment of a Photoreceptor. Human Photoreceptors (rods and cones) consist of:

• Chromophore – a small molecule called Retinal at the center that absorbs the photon. It is a type of Vitamin A.
• Opsin – a large protein that surrounds the Chromophore to shift its Absorbance Spectrum and propagate the visual signal.

In the broader sense, a chromophore is any molecule that can absorb a photon.