The invention of the scanning tunneling microscope in 1982 initiated the creation of what is known today as a whole family of scanning probe microscopies (SPMs). The importance of scanning tunneling microscopy (STM) was soon recognized and culminated in the award of half the 1986 Nobel Prize in Physics to Binnig and Rohrer. Early STM work focused mainly on the clean, bare surfaces that exist underultrahigh vacuum (UHV) conditions and provide ideal systems for formulating and testing theories of tip-sample interactions and electron transport. A great expansion of STM research was started in 1986, when Digital Instruments introduced the first commercial scanning tunneling microscope operating in ambient conditions, the NanoScope STM. The ability to perform STM work in air, under solutions, and within electrochemical cells has made the interrogation of self-assembly practical. STM can provide exquisit details on such systems, including information on electronic properties with submolecular resolution, positioning STM uniquely as tool for nanoscience.