T-PA is a protease that converts inactive plasminogen into active plasmin, which in turn cleaves fibrin, the main component of blood clots. Upon cleavage of the long fibrin strands by plasmin, the clot falls apart and dissolves. Between August 1977 and September 1978 Désiré Collen and Bjorn Wiman elucidated that the conversion of plasminogen to plasmin takes place when both proteins are bound to fibrin in the blood clot. This molecular model for the regulation and control of fibrinolysis was presented in 1979 during an invited plenary lecture (Edward Kowalski Memorial Lecture) at the VIIth International Congress on Thrombosis and Haemostasis in London. The written report of this presentation has been cited over 1200 times in the scientific literature.