  Molecules are ubiquitous in natural phenomena and man-made products, but
their use in quantum optical applications has been hampered by incoherent
internal vibrations and other phononic interactions with their environment. We
have now succeeded in turning an organic molecule into a coherent two-level
quantum system by placing it in an optical microcavity. This allows several
unprecedented observations such as 99\% extinction of a laser beam by a single
molecule, saturation with less than 0.5 photon, and nonclassical generation of
few-photon super-bunched light. Furthermore, we demonstrate efficient
interaction of the molecule-microcavity system with single photons generated by
a second molecule in a distant laboratory. Our achievements pave the way for
linear and nonlinear quantum photonic circuits based on organic platforms.
