Rinku Majumder is a biochemist, a hematologist with ~19 yrs experience in studying the roles of different clotting factors in maintaining hemostasis. Currently, her research focuses on the anticoagulant Protein S (PS). PS is a vitamin K-dependent plasma glycoprotein synthesized in the endothelium. PS deficiency is one of several known risk factors for thrombophilia and PS deficiency can increase the risk of blood clots such as Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE). In severe cases of PS deficiency, soon after birth, infants develop a life-threatening blood clotting disorder called purpura fulminans. Despite 30 years of study of this important anticoagulant, the exact role of PS is still unknown. She has recently identified a novel role of Protein S in regulating the clotting factors IXa and VIIIa independently of Activated Protein C (APC). Her recent publication in ATVB (cover page figure in October issue, 2012) demonstrated that regulation of thrombin generation via IXa/VIIIa is inhibited by Protein S. Her goal is to unravell the role of PS in regulating Thrombosis as well as Hemophilia.