This thesis concerns the manufacture and study of strongly-coupled microcavities containing a series of different organic and biological semiconductors. It contains a simple fitting model developed to describe changes to polariton population distribution observed in microcavities containing a fluorescent molecular dye. Changes are described in terms of direct radiative pumping of polariton states by weakly-coupled states coexisting within the cavity. It also describes the careful selection and characterisation of a series of molecular dyes to evaluate their likelihood of first entering the strong coupling regime and secondly producing coherent emission. The construction of a polariton laser containing one of these dyes is shown. Finally by placing a component of light-harvesting complexes (chlorosomes) harvested from bacteria within a planar microcavity, this work details the first demonstration of strong-coupling in a biological system. Further efforts to modify energy transfer in biological systems (carotenoids) by entering the strong coupling regime are discussed in detail.