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We have utilized basic principles of optical interference and resonance and applied our experience in resonant optoelectronic devices to biological applications demonstrating nanometer scale measurement capability in fluorescence microscopy and label-free sensing of protein binding in a high-throughput micro-array format. A novel application of resonance to fluorescence microscopy promises nanometer resolution in biological imaging. We have developed a technique - spectral self-interference fluorescent microscopy (SSFM) - that transforms the variation in the intensity for different wavelengths in emission of fluorophores on a layered surface to nanoscale height information. Using SSFM, we have estimated the shape of coiled single-stranded DNA, the average tilt of double-stranded DNA of different lengths, and the amount of hybridization. The determination of DNA conformations on surfaces and hybridization behavior provide information required to move DNA interfacial applications forward and thus impact emerging clinical and biotechnological fields. Recently, we have also applied SSFM to study the conformational changes of polymers and DNA-protein complexes f41.