A scanning electrochemical microscope is a scanning probe microscope (SPM). The scanning electrochemical microscopy (SECM) instrument necessarily resembles other SPM instruments, but differences in the probe tip and signal lead to differences in design and capabilities. Differences also arise from the larger amount of research and engineering development in the commercially successful atomic force and scanning tunneling microscopes. The majority of the SECM instruments in use today are custombuilt by the investigator. Although a commercial instrument dedicated to SECM has appeared on the market, both the commercial and "home-made" SECM instruments are less highly engineered than their other SPM cousins. Thus, there is still much opportunity for individual investigators to appreciate the design of SECM instruments and to make significant progress in SECM development.