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Recently, there have been innovative mechanoluminescent (ML) nano- and microparticles made available, each of which repeatedly emits light in response to small applied stresses such as deformation, friction, or impact. When dispersedly coated onto a structure, each particle acts as a sensitive mechanical sensor, while the two-dimensional emission pattern of the whole assembly reflects the dynamical stress distribution inside the structure and the mechanical information around the crack and defect. This stress visualization technique, which provides a novel way of diagnosing the structural health of a building, is advantageous over the conventional point-by-point measurement method. Recently, we have successfully exploited the remarkable advantage of the ML sensing technique by applying it onsite to a building as a non-destructive evaluation method. In this paper, we present the notable results for the visualization of active cracks on a building and the detection of crack propagation.