Colorized version of an image created by the NIST custom-built scanning tunneling microscope as it drags a cobalt atom across a closely packed lattice of copper atoms. Large round features show the cobalt atom bonding to the copper at its preferred, lowest energy bonding site. Bright triangle-shaped areas show the atoms bonding at a higher energy site. The atom "screeches in protest" when the STM tip forces it to sit at this site. Dark areas show positions that the atom "hops" over, refusing to bond at all. A scanning tunneling microscope (STM) is an instrument for imaging surfaces at the atomic level. For an STM, good resolution is considered to be 0.1 nm lateral resolution and 0.01 nm depth resolution. With this resolution, individual atoms within materials are routinely imaged and manipulated. The STM can be used not only in ultra-high vacuum but also in air, water, and various other liquid or gas ambients, and at temperatures ranging from near zero kelvin to a few hundred degrees Celsius.