Publisher Summary Various spectroscopic techniques are based on the differential interaction of left versus right circularly polarized light with molecules or molecular systems. By far, the most widely known and most often used experimental technique is that of circular dichroism (CD) in which the difference in absorption between the two different circular polarizations is measured, and for which high-quality commercial instruments for UV-visible studies are available. No commercial instruments are currently available that are specifically designed to measure the differential scattering of circularly polarized light, or the difference in intensity of left versus right circular polarization in the emission spectrum. The latter has at various times been referred to as “circularly polarized emission,” “emission circular intensity differentials,” “circularly polarized luminescence,” or, more specifically, as “circularly polarized fluorescence or phosphorescence.” This experimental technique is referred to as “circularly polarized luminescence (CPL).”