A description of the method used in the EM experiment to generate the map. SINGLE PARTICLE: reconstruction of asymmetric particles or particles with point symmetry, e.g., ribosome, GroEL, icosahedral phage FILAMENT: reconstruction of particles with helical symmetry, e.g., filamentous phage, helical acetylcholine receptor crystal 2D CRYSTAL: reconstruction of a 2D lattice, e.g., aquoporin crystal, bacteriorhodopsin crystal 3D CRYSTAL: reconstruction of a 3D lattice, e.g., yeast peroxisome crystal, acrosomal bundle INDIVIDUAL STRUCTURE (TOMOGRAM): reconstruction of a single object, e.g., bacterial cell, desmosomal knot MULTIPLE SELECTION: multiple methods used.