A revolutionary new microscope, the scanning tunneling microscope (STM), can image some surfaces at atomic resolution, even in air or water. It can produce high-resolution images of DNA, and we outline what we know of its mechanism, concluding that it may be able to sequence DNA. This application would require major advances in sample preparation in order for the technique to compete with conventional methods. On the other hand, the STM may provide a very useful alternative to gels for probing sequence-directed structural features.