The structure of contracted human whole blood clots by confocal light microscopy. (A) Confocal light micrograph of contracted whole-blood clot activated by thrombin following recalcification. Erythrocyte membranes of 30% of cells were fluorescently labeled with DiD. (B) Whole blood before clotting. Leukocytes and platelets were labeled with calcein (green); larger cells are leukocytes and smaller ones are platelets. Fibrinogen was labeled with Alexa 564 but is not visible, because it is not polymerized. (C) Three-dimensional reconstruction of contracted whole-blood clot. The outside of the clot is on the top, where there are platelets (green), fibrin (red), and biconcave erythrocytes (white). Erythrocytes deeper in the clot are polyhedral. Magnification bar = 25 µm.