Final answer:
Fluorescent molecules absorb light at the excitation wavelength and emit light at a different color or wavelength, which is known as the emission wavelength. This is why the excitation and emission light in experiments using fluorophores to highlight cell components are different colors.
Step-by-step explanation:
Fluorescent molecules have characteristic emission and excitation spectra, which are determined by their electronic energy levels. When a fluorescent molecule absorbs light at the excitation wavelength, the electrons in the molecule become excited and move to higher energy levels. As the electrons return to their ground states, they emit light at a lower energy level, which corresponds to a different color or wavelength. This is why the excitation and emission light in experiments using fluorophores to highlight cell components are different colors.