In the framework of the funding program for France-Finland cooperation between the Institut Français in Finland, the Finnish Society for Science and Letters and the French Ministry of Higher Education, Research and Innovation, professor Benoît Perthame, mathematician and professor at the Pierre-et-Marie-Curie University and director of the Jacques-Louis Lions laboratory, was invited in Finland to take part in the Finnish Mathematical Days 2018 on the 4th and 5th of January in Joensuu. This weekend was co-organized by the Finnish Mathematical Society, the European Mathematical Society and the European Society for Mathematical and Theoretical Biology. These meetings are organized every second year as an exhibition of Finnish mathematics research and education.