There are two main interests in the research carried out by Professor Guillermo Restrepo: mathematical chemistry and philosophy of chemistry. His mathematical approaches to chemistry have been through discrete mathematics, especially graph and order theory and point-set topology. This research has led him to estimate properties of substances, to assess environmental targets, and to find novel structures of chemical constructs such as the periodic system of chemical elements. His questions in philosophy of chemistry have to do with the mathematical way of thinking and its realization in chemistry. Professor Restrepo is Fellow of the Alexander von Humboldt Foundation/Stiftung, member of the International Academy of Mathematical Chemistry, and of the Executive Committee of the International Society for the Philosophy of Chemistry. He is also a member of the editorial board of MATCH Communications in Mathematical and in Computer Chemistry, and of Hyle -- International Journal for Philosophy of Chemistry.