This article provides an introduction to scanning ion microscopy, explaining how it overcomes one of the biggest limitations of SEMs, namely the tradeoff between spatial resolution and depth of field, while also providing significantly more surface detail, a wide range of novel and familiar contrast mechanisms, and the potential for new microanalytical techniques that combine nanometer spatial resolution and single monolayer sensitivity. In addition to describing the capabilities of scanning ion microscopes, the article also addresses the issue of sample charging and the potential for physical damage that can result from ion beam irradiation.