Coherent anti-Stokes Raman scattering (CARS) microscopy allows viewing of live biological samples -- without photoluminescent labeling or staining -- by using three laser beams to induce electromagnetic vibrational signals from a sample. However, it often produces unwanted background signals from the sample and its surrounding solution.Using the time-resolved microscopy technique to record the decay of the net polarization of molecular vibrations in the sample, researchers from Harvard University in Cambridge, Mass., filtered out the background signals by isolating the resonant contribution of the decay and using it as the basis of imaging -- thus increasing the detection sensitivity of the method.As reported in the March 4 issue of Applied Physics Letters, tests of the procedure yielded background signals suppressed by a factor of approximately 570.