Analyses of papyrus plants (Cyperus papyrus L.) from the Botanical Garden of the University of Genova and Ciane River (Siracusa) were used as a basis for the detection of histological features in papyrus paper. Both modern and ancient papyrus papers were analysed. Modern papyrus were manufactured at “Museo del Papiro di Siracusa”; two types of ancient papyrus (Egyptian and Greek–Roman, from Cairo Archaeological Museum) were studied. Sections of paper and plant stalks, taken 20 cm from the top, were examined under a scanning electron microscopy (SEM) and optical microscope (OM). The lignificated parts of both the plant and paper were either red (using acid flouroglucine) or blue–green (using Toluidine Blue) and were refracting under polarised light microscopy. Calcium oxalate crystals and starch granules were also detected. It was clear that the ancient Egyptian paper is richer in starch in comparison to the Roman one. It could be presumed that the Egyptian paper contains starch, a material which naturally occurs in the plant as a reserve. It was, in fact, preferably found in the residuals of the vascular bundle sheath. Microscope observations were compared with the results obtained by thermal and calorimetric analyses (TG and DSC). Thermal curves were different depending on which part of the plant was used to manufacture the papyrus and probably depend on the amount of cellulose and lignin present. Moreover, the Egyptian and Greek–Roman were also different in thermal behaviour.