During the early stages of CDSA, the platelet size is below the diffraction limit, and thus platelet area cannot be used to examine growth kinetics. However, the evolution of particle contrast can be used to report on this early stage (Figs. &). As platelets are detected, individual spots begin to appear on the surface with their absolute contrast values increasing over time (becomes more negative, i.e., darker). Eventually, these diffractionlimited spots grow sufficiently that the characteristic shape becomes discernible (Fig. ).