The use of optical imaging is a very significant tool in biological discovery. A need exists for the multiplexed detection of disease biomarkers. At present, these tags are based on SERS, whose sensitivity depends largely on the Raman signal strength of the Raman reporter, most of which are organic compounds whose signals overlap with those of the cells. We have developed a class of imaging tags based on organometallic compounds in recent years, particularly transition metal carbonyl compounds. As these compounds exhibit strong absorption bands in the mid-IR, around 2000 cm-1, for the CO stretch, they are advantageous for imaging cells since they do not interfere with the absorptions of the contents of the cells. During this presentation, we will cover recent developments in SERS as a biosensing and bioimaging technology. In addition to a brief overview of SERS, the underlying mechanisms of Raman enhancement will also be discussed. Clinically relevant OM based SERS-active plasmonic nanomaterials will be discussed in terms of their design and sensitivity. Afterwards, imaging and biosensing applications will be explored.