Numerous scanned probe microscopes (SPM) have been developed over the past decade. Most are based on the precise positioning of sample and probe using piezoelectric transducers, and some have the capability of imaging flat surfaces with atomic resolution. The first atomic resolution SPM applied to biological samples was the scanning tunneling microscope (STM). The atomic force microscope (AFM) was subsequently developed and over the past few years has become the instrument of choice for biological applications.