Papers presented at 21st Symposium for the Study of Underdrawing and Technology in Painting, held in Brussels on 12-14 September 2018. Here on the Düsseldorf coloured drawing of the Dulle Griet, which was examined at the Royal Institute for Cultural Heritage (KIK-IRPA) in Brussels in collaboration with the Kunstpalast, Düsseldorf, using infrared reflectography, infrared photography, transmitted light photography, macro-XRF and micro-Raman spectroscopy. The study of the paper revealed the watermark of Niklaus Heusler, a Basel paper manufacturer, giving 1578 as the earliest possible execution date for the drawing, and thus confirming its status as a copy. Examination and analysis of the colours suggest that they are most likely original. Various hypotheses are proposed as to the drawing's original function, attribution and context, taking into account the early history of Bruegel's Dulle Griet. Thanks to its early dating, the drawing is a key witness to the appearance of the Dulle Griet painting at an early stage in its history, and as such it provided fundamental help during the conservation campaign. Certain colours and motifs that have altered over time in the painting remain more legible in the drawing.