chromophore

thumb|Leaves change color in the fall because their chromophores (chlorophyll molecules) break down and stop absorbing red and blue light.

A chromophore is the part of a molecule responsible for its color. The word is derived . The color that is seen by our eyes is that of the light not absorbed by the reflecting object within a certain wavelength spectrum of visible light. The chromophore is a region in the molecule where the energy difference between two separate molecular orbitals falls within the range of the visible spectrum (or in informal contexts, the spectrum under scrutiny). Visible light that hits the chromophore can thus be absorbed by exciting an electron from its ground state into an excited state. In biological molecules that serve to capture or detect light energy, the chromophore is the moiety that causes a conformational change in the molecule when hit by light. alt=|thumb|Healthy plants are perceived as green because chlorophyll absorbs mainly the blue and red wavelengths but green light, reflected by plant structures like cell walls, is less absorbed. alt=|thumb|upright=1.35|The eleven conjugated double bonds that form the chromophore of the beta carotene|β-carotene molecule are highlighted in red.