In 1920 Hermann Staudinger suggested that polymers were formed through covalent bonds (H. Staudinger; Über Polymerisation. Ber. Dtsch. Chem. Ges. 1920, 53, 1073), and used the term "makromolekel" (macromolecule) in 1922 (Staudinger, H. and Fritschi, J. (1922), Über Isopren und Kautschuk. 5. Mitteilung.† Über die Hydrierung des Kautschuks und über seine Konstitution. HCA, 5: 785-806. https://doi.org/10.1002/hlca.19220050517). This session of Polymer Café will highlight and discuss these groundbreaking works. The discussion lead is prof. Seb Perrier.