From an experimental perspective, the task requires a method that enables the decomposition of the overall decoherence into individual contributions by chemical groups. This is beyond what can be done using optical absorption or fluorescence, photon-echo and even multidimensional laser spectroscopies. To varying extents, these techniques enable characterizing the overall decoherence time scale and the molecular Hamiltonian, but do not offer means to disentangle the contributions by specific functional chemical groups. From a theory perspective, the challenge is that accurately capturing the decoherence requires a fully-quantum quantitative description of the energetics and dynamics of the molecule in its chemical environment, and the computational cost of doing so increases exponentially with the size of the molecule and the environment. For this reason, most of our theoretical understanding of decoherence arises from model problems that, while extremely useful, do not fully capture the complexities of realistic chemical systems. For instance, recent efforts to quantify electronic decoherence by explicitly propagating multidimensional quantum dynamics of molecules have so far been limited to systems at zero temperature and in vacuum, and thus are not informative of quantum decoherence in solvent and other condensed phase environments. In turn, efforts to include the influence of thermal environments implicitly through numerically exact quantum master equations, such as the HEOM and TEMPO , have thus far been mostly limited to simple models that do not necessarily capture the complexity of chemical environments. Specifically, in quantum master equations the interaction between the molecular chromophore and its thermal environment is characterized by a spectral density, J(ω) , which quantifies the frequencies of the nuclear environment, ω, and their coupling strength with the electronic excitations. Unfortunately, the quantitative determination of J(ω) has remained elusive to theory , and its experimental characterization is limited. For this reason, most studies of molecular decoherence based on quantum master equations rely on simple models of the spectral density that do not capture the interactions of realistic chemical problems. Here we introduce a general strategy to quantitatively characterize the electronic decoherence dynamics of molecules in realistic chemical environments and to map decoherence pathways, see Fig. . The strategy is based on reconstructing the spectral density J(ω) from resonance Raman experiments and decomposing the overall coherence decay into contributions by individual vibrational and solvent modes. Using this strategy, we can now address previously inaccessible questions, such as the interplay of solvent and vibrational contributions and the influence of chemical substitution on quantum decoherence. The reconstructed spectral densities open opportunities to investigate molecular decoherence dynamics in realistic chemical environments using stateof-the-art methods in quantum dynamics. Further, the overall strategy connects chemical structure to quantum decoherence dynamics and opens unique opportunities to develop the chemical principles of quantum decoherence.