The main purpose of haemostasis, the formation of a blood clot composed of activated blood platelets intertwined with covalently linked fibrin, is arrest of bleeding from a damaged blood vessel. Thrombin is a multifunctional serine protease produced from prothrombin and is a key regulator in haemostatic and non-haemostatic processes. Thrombin activates platelets through PAR1 or -4, providing a procoagulant phospholipid membrane surface on which coagulation factors congregate. With multiple functions, thrombin is considered the central enzyme in coagulation. Not only does thrombin convert fibrinogen into fibrin, it enhances its own generation through activation of the cofactors V and VIII as well as factor XI in the so-called feedback loop. Through activation of factor XIII, thrombin stimulates covalent crosslinking of fibrin molecules. Thrombin attenuates its own generation through activation of the protein C pathway, in which thrombomodulin bound thrombin activates protein C on the endothelial protein C receptor.1.Posma JJ, et al. J Thromb Haemost. 2016;14(10):1908–1916.