Strong coupling between excitons and photons inside a microcavity leads to the formation of cavity polaritons, hybrid light-matter particles. Under suitable conditions, polaritons can emit coherent light without population inversion, whereby polariton lasing can exhibit a threshold at least an order of magnitude less than that of conventional photon lasing in the same material. Polaritons in organic semiconductors are stable at room temperature, due to their large exciton binding energy. This renders organic materials interesting for light-mater interaction experiments at ambient conditions. In this paper, we report on polariton-lasing using fluorescent proteins embedded in a planar microcavity. The typical laser-like threshold-behavior, manifesting in an intensity nonlinearity, coherence build-up with a linewidth drop and an interactioninduced blueshift stemming from the part-matter nature of polaritons are presented. Additionally, we show the possibility to confine photonic modes inside deterministically created traps by presenting discretized mode spectra.