The cover picture shows thrombin-specific substrates bound in the active site of thrombin. In the background, the intact fluorogenic conjugate (shown in yellow) of thrombin-specific tripeptide H-Gly-Gly-Arg and 7-amino-4-methylcoumarin (AMC) bound to thrombin is displayed. Prior to thrombin-mediate hydrolysis, this substrate displays only weak fluorescence. Upon cleavage of the ArgAMC bond, strongly fluorescent AMC (shown in bright blue) is liberated. Quantification of the increase in fluorescence over time provides a direct measure for the amount of thrombin present in plasma. Moreover, from these data, the specific thrombin activity can be calculated, which is a direct measure of the coagulability of a clotting sample. These substrates have potential application in microfluidic devices for point-of-care tests, allowing the rapid diagnosis of blood or plasma samples. For more details, see the Full Paper by Floris P. J. T. Rutjes et al. on p. 606 ff.