Organic molecules interact strongly with confined electromagnetic fields in plasmonicarrays or optical microcavities owing to their bright transition dipole moments. Thisinteraction gives rise to molecular polaritons, hybrid light-matter quasiparticles.Molecular polaritonics opens new room-temperature opportunities for the nontrivialcontrol of energy transport in the nano and mesoscales and modification of physicochemicalproperties of molecular assemblies. In this talk, I’ll showcase some of theseopportunities that we have been theoretically exploring in the past few years within thecontext of physical chemistry. I’ll start by briefly mentioning our work on topologicallynontrivial phases in excitonic and polaritonic systems of organic dye molecules [1,2].Next, I will discuss recent work on how polaritons can enhance singlet-fissionprocesses  or how excitation energy can be transferred across mesoscopicdistances of hundreds of nanometers to micron lengthscales . If time permits, I’llconclude by explaining what we can learn about molecular polaritons using twodimensionalspectroscopy [5,6]. J. Yuen-Zhou et al., Nature Mater. 13, 1026 (2014). J. Yuen-Zhou et al., Plexcitons: Dirac points andtopological modes, Nat. Commun. 7, 11783 (2016). L. A. Martínez-Martínez, et al., Polariton-assistedsinglet fission in acene aggregates, under review in J.Phys. Chem. Lett., arXiV:1711.11264. M. Du et al., Polariton-assisted remote energy transfer(PARET), under review in Chem. Sci., arXiv:1711.11576. B. Xiang et al., Revealing hidden vibration polaritoninteractions by 2D IR spectroscopy, under review in Proc.Nat. Acad. Sci., arXiv:1711.11222. R. F. Ribeiro et al., Theory for nonlinear spectroscopyof vibrational polaritons, submitted to J. Phys. Chem.Lett., arXiv:1711.11576.