Atomic force microscopy and scanning tunneling microscopy were used to obtain molecular resolution images of biological structures such as proteins and viruses. Proteins of 10 to 20 nm scale could be reliably resolved with faintly recognizable subunit arrangements. Bacteriophage T4 was imaged with well-resolved head, tail, and tail fibers. When the tails were prepared from the headless mutants, the sheath proteins were stripped away from the tail, revealing the tube and the base plate in a T-shaped complex. Scanning tunneling microscopy was used on metal coated samples and provided a reliable height measurement for bacteriophage T4. Constant improvement in the instrumentation and sample preparation promises a bright future for the biomedical application of scanning probe microscopy.