摘要： Superresolution in microscopy has intrigued researchers for many years. There is always a challenge in overcoming what seems to be a fundamental limit. Even since the award of the Nobel prize in Chemistry in 2014 for stimulated emission depletion (STED) microscopy and localization microscopy, there has been continuing activity to improve these techniques, by reducing specimen radiation exposure for example. The term superresolution refers to overcoming the classical limit to resolution, usually defined in terms of either the Abbe resolution limit, or the Rayleigh two-point resolution criterion. These two measures are robust, the Abbe limit in particular providing a hard limit that can only be beaten by a fundamentally new approach, almost like a ‘trick’. Rayleigh recognized that his criterion was arbitrary, but considered it robust enough. Originally defined for incoherent imaging of self-luminous objects, its applicability has been extended to coherent and partially coherent systems, and later to confocal microscopy and other developments. This is usually achieved by the so-called ‘generalized Rayleigh resolution criterion’, according to which two points are taken as being just resolved when the intensity of the image midway between the points is 0.735 times that at the points themselves. It is found that around this value the image contrast changes quickly for a small change in the separation of the points.