Invading microorganisms release longer polyP polymers whereas activated platelets release shorter polymers (60-100 mer) or very short phosphates (pyrophosphate). Longer polymers (1000+) are very effective in activating the contact pathway of coagulation whereas shorter polymers (60-200 mer) are more effective in activating FV; ≥ 250 mer support maximal fibrin clot turbidity. Pyrophosphate released by platelets can block polyP-induced fibrin clot turbidity. Very short polymers (10-80 mer) can inhibit the contact pathway activation initiated by long-chain polyP. The polymers shown in the figure represent ∼ 1000+ mer, 250+ mer, 60-250 mer, 10-60 mer, and very short phosphates (mono-, pyro-, and triphosphates). The green arrows direct to the point in the clotting cascade that is shown to be affected maximally by the specific range of polymer size. (Professional illustration by Paulette Dennis.)