There are many applications that demand that the properties of light be controlled by molecular excitons. This includes upconversion applications, where shorter wavelengths are generated from longer wavelengths using triplet fusion, and multiple exciton generation due to singlet fission, where a high energy photon is split into smaller energy packets. In these conjugate processes, an excited state chromophore is necessarily in contact with one or more ground state chromophores, opening up the possibility of excimer formation. What is the role of the excimer in these systems? Is it a trap, or is it an intermediate? By careful analysis of time-dependent photoluminescence and absorption spectroscopy, and consideration of thermodynamical principles, we have concluded that excimers play no useful role at all in the solution phase,1,2 despite claims to the contrary.3,4 A more recent report confirmed an emissive triplet fusion intermediate in the solid state.5 Where does that leave solutions? We carefully analysed the room temperature time-resolved emission of a neat liquid singlet fission chromophore. It exhibits three spectral components: two that correspond to the bright singlet and excimer states, and a third component that becomes more prominent during triplet fusion. This spectrum is enhanced by magnetic fields, confirming its origins in the recombination of weakly-coupled triplet pairs. It is tentatively attributed to strongly coupled triplet pair state. These observations unite the view that there is an emissive intermediate in singlet fission and triplet fusion, distinct from the broad, unstructured excimer emission. This talk will conclude with a short update on silicon-based singlet fission solar cells being developed at UNSW, and other interesting happenings.