The morphology of platelets in platelet-rich plasma (PRP) change as a function of bench set time. Centrifuged blood was allowed to set on the bench for up to 6 hours, and then PRP was harvested at various times. Samples were smeared, stained with Wright-Giemsa, and viewed/photographed using brightfield microscopy. All fields are ×1000 magnification. (A) Whole blood; note that very few platelets are present relative to the number of red blood cells (RBCs). (B) A 0 bench set time; note that the platelets are higher in number relative to the RBCs, indicating that platelets have been enriched using the procedures described previously. Also note that the platelets possess a normal morphology (discoid, light blue staining, with little to no adherence to one another [aggregation]). (C) A 30-minute bench set time; concentrated platelets continue to appear intact and healthy. (D) A 1-hour bench set time; platelets begin to aggregate but they are still ovoid and lightly stained. (E) A 2-hour bench set time; platelets form larger aggregates and have begun to lose ovoid shape developing bleb-like structures on the plasma membranes. (F) A 6-hour bench set time; note the aggregation occurring with prolonged bench set time with more than 100 platelets per aggregate. Platelets appear shrunken and misshapen, suggesting a loss of functional capacity.