  The article demonstrates some less known principles of image build-up in
diffractive microscopy and their usage in analysis unravelling the smallest
localized information about the original object - an electromagnetic centroid.
In fluorescence, the electromagnetic centroid is naturally at the position of
the fluorophore. The usage of an information-entropic variable - a point
divergence gain - is demonstrated for finding the most localized position of
the object's representation, generally of the size of a voxel (3D pixel). These
spatial pixels can be qualitatively classified and used for reconstruction of
the 3D structures with precision comparable with electron microscopy.
