Outline of correlation of confocal and EM images. Three-dimensional (3D) reconstructed confocal data of the pretangles were obtained from a free-floating section. After landmarks were punched out around the target neuron using laser microdissection, sections were fixed and embedded in epon: the section was gently pressed between aclar films, hardened, then stuck to the columnar epon prepared in advance. The epon block was trimmed by the guidance of landmarks around the neuron, and ultrathin section of the block were examined with electron microscopy (EM). After obtaining the most appropriate EM images, their exact light microscopic counterparts were retrieved from the corresponding fluoresent 3D data set for direct comparison.