Depending on the timescale of this solvent reorganisation event, 𝜏 R -and the lifetime of the excited state, 𝜏 F -any fluorescence emission resulting from excitation of Microenvironment A can therefore depend upon excitation wavelength. For the case where solvent relaxation is much faster than the fluorescence lifetime (𝜏 F ≫ 𝜏 R ), excitation of Microenvironment A results in emission that always occurs from the relaxed solvent configuration in S1, and emission is excitation-wavelength independent. However, for solvent relaxation timescales that are much longer than the fluorescence lifetime (𝜏 F ≪ 𝜏 R ), or are close in timescale (𝜏 F ≈ 𝜏 R ), fluorescence occurs from unrelaxed solvent configurations, allowing for wavelength-dependent emission, with this also applying to the excitation spectrum. Now less abundant microenvironments can be considered, as thermal energy and other external forces allow for unrelaxed S0 states to exist without any photoexcitation. One such case, labelled Microenvironment B (Figure bottom) is important, as photoexcitation here results in the already relaxed state of S1 (Figure top). The consequence of this higher energy S0 and lower energy S1 for Microenvironment B, is that these excitations can be exclusively accessed with longer excitation wavelengths that are incapable of exciting the more abundant microenvironments that exist at Microenvironment A and range in energy difference up to Microenvironment B. These microenvironments become fewer as the energy of S0 increases, this is seen in the absorbance spectrum as lower values of absorbance at the red-edge (Figure ). Importantly, access to certain excited-state geometries, and resulting longer wavelength emissions, is therefore exclusive to longer excitation wavelengths, while shorter excitation wavelengths are instead most likely to excite those abundant microenvironments that are unable to reach excited states with relaxed solvation (for cases when 𝜏 F ≈ 𝜏 R or 𝜏 F ≪ 𝜏 R ) before they fluoresce (Figure ). Interestingly, selective excitation of chromophores with wavelength is not the only possibility due to these phenomena. In addition, the subset of chromophores that are selectively excited also display unique properties from those in the bulk solution, with both fluorescence emission and excited-state lifetime becoming wavelength dependent. Not only are certain chromophores selectively excited, but these specific chromophores can also experience unique excited-state dynamics, allowing for variations of photophysical processes within a bulk solution, without violating general rules such as Kasha's rule. It is this influence of a wavelength-dependent selection of specific microenvironments and the ensuing effects on the resulting photophysical processes, that we suggest ultimately impacts upon wavelengthdependent photochemical reactivity, and that this paper seeks to investigate.