Scanning electron microscope images of clots and thrombi. In vitro clots made from human (A) platelet-poor plasma and (B) platelet-rich plasma. (C) The fibrin formed on a surface coated with collagen-adherent platelets is made up of many fibers aligned along the direction of flow. (D) The image shows an ex vivo human coronary artery thrombus obtained by aspiration from a patient with ST-elevation myocardial infarction. Magnification bars represent 10 μm.