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The problem illustrated above is that the fluorescent signals of adjacent objects overlap if they are closer than the limit set by diffraction, which is why two adjacent fluorophores seem to form a single spot in panel B. SMLM solves this problem by imaging the fluorophores one at a time. It does this by ensuring that in each image, light is only emitted from a few sparsely distributed fluorophores, which are can then be precisely localised . Another set of fluorophores are localised without their emission overlapping with that of a neighbour. The fluorophores only emit for a short time, so in the next image and this a different set of fluorophores is localised. This process is then repeated, usually for >10000 images .The above case is relatively trivial because there are very few molecules and they are well spaced apart. In fluorescently labelled cells the problem is usually more challenging because there are more fluorescently labelled molecules and they are crowded together in higher order structures like organelles, membranes, etcand final super-resolution image is constructed from all the precise localisations. The on/off switching of fluorophores between frames is often described as 'blinking'. SMLM techniques mainly differ in how the blinking is achieved.