Histograms showing the percentage of fibrin structures visualized by electron microscopy at 1, 3, 6, and 9 minutes during fibrin polymerization. All types of structures that appear in the images were counted in each micrograph. The number of monomers within each type of structure was calculated and normalized by the number of monomers present in the whole micrograph. Structures can be identified as: (A) fibrin monomers, (B) dimers, (C) trimers, (D) tetramers, (E) larger oligomers and protofibrils, and (F) fibers.