Trapping light waves as a result of their resonant interaction with free electrons in the conduction band of metals is the concept behind several emerging nanophotonic technologies. The localization of surface plasmons using engineered metal nanostructures and their interaction with molecular polarizability tensors have afforded single molecule detection sensitivity in surface-enhanced Raman scattering (SERS), and more recently, chemical imaging within one molecule through tip-enhanced Raman scattering (TERS). Single molecule detection sensitivity can be achieved by taking advantage of electromagnetic enhancement factors exceeding 10¹⁰, amenable at plasmonic nanojunctions where molecules are sited and interrogated. This talk will highlight some of the operative mechanisms which govern optical spectroscopy at plasmonic nanojunctions, and their impact on what is experimentally observed in SERS and TERS. The concepts will be illustrated through model studies which take advantage of a wealth of microscopic, spectroscopic, and computational tools available at PNNL. Results of correlated scanning electron and photoemission electron microscopy experiments, correlated AFM/Raman measurements, as well as on on-going efforts to push the limits of sensitivity and resolution in TERS will be discussed.