TERS - To improve the spatial resolution down to a nanometer scale, the SERS technique is combined with AFM. This technique is known as Tip Enhanced Raman Scattering (TERS). The AFM tips are coated with silver resulting in SERS active silver particles at the top of a tip. Spectra with a good signal-to-noise ratio can be measured on bacteria by means of TERS. With this method the fluctuation of different outer cell wall components are detectable.