A scanning tunneling microscope (STM) is a powerful tool used to visualize surfaces at the atomic level. It works by scanning a sharp metal tip very close to a conductive surface. When the tip is near enough, electrons can "tunnel" between the tip and the surface, creating a measurable current. This current is used to create detailed images of the surface's atomic structure. STMs are essential in fields like nanotechnology and materials science, allowing researchers to study the properties of materials at an unprecedented resolution. They can also manipulate individual atoms, making them valuable for developing new technologies and understanding fundamental physical processes.