Thromboelastometry (ROTEM®) is an advancement of the classical thrombelastography (TEG), first described by Hellmut Hartert in 1948. Since then, several technical enhancements made the device more robust and user-friendly, reduced intra- and inter-operator variability, and improved the diagnostic performance. Since coagulation factor concentrates such as fibrinogen concentrate and prothrombin complex concentrates (PCCs) are licensed for bleeding management due to hereditary and acquired coagulation factor deficiencies in Germany for more than 20 years, the ROTEM® delta device and assays have been designed to identify specific coagulopathies in real time and to guide hemostatic therapy most specifically with coagulation factor concentrates (e.g., fibrinogen concentrate, PCCs, factor XIII concentrate, and recombinant activated factor VII) and other blood products (e.g., fresh frozen plasma, cryoprecipitate, and platelets). The combination of specific ROTEM® assays improves the diagnostic performance significantly. The “blind spot” of viscoelastic testing—platelet dysfunction due to antiplatelet drugs or other clinical conditions such as trauma, cardiopulmonary bypass, and sepsis—could be covered by the ROTEM® platelet module using the well-established whole blood impedance aggregometry technology. As an essential part of a “patient blood management” program, the concept of thromboelastometry-guided bleeding management aims to stop bleeding as soon as possible and to avoid any unnecessary or inappropriate blood transfusion, which is known to be associated with severe adverse events. Accordingly, the implementation of thromboelastometry-guided bleeding management algorithms (“theragnostic approach”) has been shown to reduce transfusion requirements, transfusion-associated adverse events, patient’s morbidity and mortality, as well as hospital costs in several clinical settings. This concept is also gaining acceptance and recommendation in the USA, e.g., in the recently published “practice guidelines for perioperative blood management” from the “ASA Task Force on Perioperative Blood Management.” The characteristics of thromboelastometry allows for using the device at the bedside in the emergency department, the operating room, and the intensive care unit in a mobile way and in a multiuser environment, even in military settings. This could be further optimized by developing a fully automated thromboelastometry device, the ROTEM® sigma, which is a cartridge-based system with lyophilized reagent beads not requiring pipetting but still using the proven pin-and-cup technology.