In the Spring it was exactly 400 years since the death of the mathematician Simon Stevin (1548-1620). To commemorate the death of this famous historical figure, the exhibition 'Simon Stevin van Brugghe, 1620-2020. Hij veranderde de wereld' [He changed the world] ran in his hometown Bruges in 2020. In order to better understand the world in which Stevin lived and wrote, five flemish heritage libraries assessed their collection of early printed books in the field of mathematics. The Hendrik Conscience Heritage Library was one of the partners participating in this collection assessment project.