Immunogold Annexin V–labeling and FIB-SEM imaging of the PS-positive platelets, and of the “caps.” (A) Immunoelectron microscopy of Annexin V binding to platelets; the left panel shows increased magnification. (B) FIB-SEM imaging (left) and 3D-reconstruction (right) of the procoagulant platelets. The arrows indicate Annexin V on the platelet “cap.”