Induction of DNA damage elicits a complex set of reactions in a mammalian cell, including signaling, recruitment and accumulation of repair factors at the site of damage, undertaking restoration of the original DNA sequence and chromatin higher order structures, and disengagement of the repair factors after completion of the these processes. The recruited repair proteins form a so called repair focus – an assembly of a large number of factors associated with the DNA lesion or a cluster of lesions. It has emerged recently that the recruited repair factors are highly dynamic and that their spatial positions in some repair foci formed in response to double strand DNA breaks are not random, but convey an ordered internal architecture of these ensembles. Contemporary fluorescence microscopy, in all its various embodiments, including live cell imaging, particle tracking, super-resolution imaging, fluorescence correlation spectroscopy and other methods have opened new avenues to understanding the mechanisms and spatial organization of DNA repair processes. I will introduce newly optimized laser scanning microscopy-based techniques of detecting low level DNA damage, involving a novel method termed STRIDE, an ultra-sensitive fluorescence microscopy technique of detection of various types DNA lesions (including the ones induced by CRISPR/Cas9 nuclease and its nickase variant), and will discuss dynamics of the recruited repair proteins (XRCC1, 53BP1) and the architecture of repair foci in the context of repair efficiency and choice of the repair pathway.