In microscopy, the term ‘resolution’ is used to describe the ability of a microscope to distinguish detail. In other words, this is the minimum distance at which two distinct points of a specimen can still be seen – either by the observer or the microscope camera – as separate entities. The resolution of a microscope is intrinsically linked to the numerical aperture (NA) of the optical components as well as the wavelength of light which is used to examine a specimen. In addition, we have to consider the limit of diffraction which was first described in 1873 by Ernst Abbe. This article covers some of the history behind these concepts as well as explaining each using relatively simple terminology.