The Nobel Prize-awarded invention of the scanning tunneling microscope (STM) has profoundly revolutionized contemporary science and technology. The STM has enabled individual atoms and molecules to be imaged, probed and handled with an unprecedented precision, thereby essentially contributing to our current understanding of the world at the nanoscale. Together with its offspring, the atomic force microscope (AFM), the STM is considered as the main innovation behind the birth of nanotechnology. This chapter is an elementary introduction to STM and to its most recent uses. Topics include a basic treatment of the underlying theory of tunneling, the description of the most commonly used experimental setups, a survey of the atomic-scale spectroscopic capabilities (scanning tunneling spectroscopy, STS) and an overview of atomic manipulation experiments.