This was the historical and cultural context that framed the work and studies of a young German physiologist, Dr. Hellmut Hartert (1918 Tübingen – 1993 Kaiserslautern). He started his research from the two main limitations of PT and aPTT: (a) these tests evaluated only the initiation of the clotting process; (b) the information obtained was limited to plasma.

Dr. Hartert conceived the first thromboelastograph in Germany, in 1948 [6]. He started from the concept that blood clot has both viscous and elastic properties. Based on these premises, he developed an apparatus able to measure the elastic shear modulus or storage modulus of clotting blood. The method provided that an aliquot of whole blood be placed in the sample cup. A pin suspended by a calibrated torsion wire was lowered into the sample. To measure the elastic shear modulus of the sample, the cup was oscillated through an angle of 4° 45″ over a 10s interval, including 1s rest periods at the end of the rotation in each direction to prevent viscosity errors. The torque of the cup is transmitted to the pin through the sample in the cup. The width of the tracing is proportional to the magnitude of elastic shear modulus of the sample that is affected by platelet count and fibrinogen levels in whole blood [7]. Thromboelastographic information was obtained from an uninterrupted recorded tracing called the thromboelastogram. At the very beginning, only reusable steel sets of cups and pins were available and whole blood (350 uL) containing no anticoagulants would be placed directly in the instrument immediately after being drawn with the sample being recalcified to start the procedure. In 1974, Caprini [8] and colleagues introduced a modified technique called celite-activated TEG, consisting of comparing two simultaneously performed thromboelastograms: one was a native whole-blood thromboelastogram and the other was performed in native whole-blood activated with celite.