Number 308 (Story #1), February 20, 1997 by Phillip F. Schewe and Ben Stein SURFACE ENHANCED RAMAN SCATTERING (SERS) can be used to detect single molecules. In Raman spectroscopy the light scattered inelastically from a molecule provides information about the molecule's vibrational quantum states. The rather weak Raman effect can be greatly strengthened (by a factor of up to 14 orders of magnitude) if the molecules are attached to nm-sized metal structures. (The way in which the enhancement occurs is still not known for sure.) In this way, an MIT-Berlin group (Katrin Kneipp, 100342.530@compuserve.com) has detected single dye molecules attached to colloidal silver particles in an aqueous solution. The advantages of this method are that it is fast, it can supply some structural information about the molecules, and it doesn't bleach the molecules. Single-molecule detection is of great practical interest in chemistry, biology, and medicine, and pollution monitoring; examples include DNA sequencing and the tracing of biomedically interesting molecules. (Kneipp et al., upcoming article in Physical Review Letters.)