The proposed research program builds on the previously developed ultra-high-Q monolithic micro-resonators by the applicant during his dissertation at the “California Institute of Technology”. These micro-resonators offer unprecedented confinement of light in micro-scale volumes for extended amounts of time and have opened many lab-on-chip applications ranging from nonlinear optics, quantum optics to biochemical sensing. This present proposal is concerned to use ultra-high-Q optical micro-cavities as vehicles to study two novel and emerging research opportunities. The first endeavor investigates the possibility to use radiation pressure to cool a mechanical oscillator to the quantum ground state. The significance of the research program lies in its attempt to exploit the opto-mechanical system as a paradigm for the investigation of quantum processes of mechanical objects – a field which has sparked widespread interest in contemporary physics for quiet some time, but which to date remains experimentally unexplored and which is intimately related to concepts used in fields such as gravitational wave detection or scanning probe techniques. From a conceptual point of view, this research could show how a mechanical, macroscopic object reveals quantum mechanical behavior. Ultra-sensitive measurements are also part of a second, interdisciplinary line of research. To date, only a few widely applied techniques in Biophysics are available for label free detection of ligand-receptor binding, which lack single to resolve single molecule binding events. Building on recent advances of the applicant, the proposed methodology will use membrane functionalized micro-resonators in aqueous solution as novel technique to resolve single binding events. By developing a methodology with which label free single molecule sensitivity in biomolecular recognition can be attained, this research could enable to open new frontiers to Biophysicists.