The excited energy states of the nitrogen nucleus.
This beautiful optics table took two years to build. It exists in the physics department basement. Quite a few different colours (or energies) of laser light are required to cool a molecule due to the more complex energy level structures (compared with an atom) - resulting in this lovely spectacle. The molecules are cooled to temperatures colder than outer space of less than a mK by hitting them with carefully tuned photons of light that exactly match the quantum energy levels of the molecule taking into account the doppler effect.