The population transfers among polariton states in the works mentioned above are rationalized by considering their relative energetic ordering such that population dynamics flow downhill, which is reminiscent of Kasha's law. Based on this picture, for a typical energetic ordering of polaritonic states shown in Fig. , we anticipate a relatively small upper polariton population and a relatively large lower polariton population. Ref. 427 points out that this picture of energetic downhill population dynamics could be misleading as it ignores the entropic contribution which could make a dominating contribution to the free energy and dictate long-time populations. For example, while lower polaritons can lie energetically well below the dark states, the entropy of the lower polariton (that is in a delocalized superposition state) is much smaller than that of the localized (localized especially when considering disorder) dark states. Thus the total free-energy F = E -T • S, with temperature T , energy E and entropy S may reorder polaritonic states as shown in Fig. .