Leila Lazemi and Stephan Weber participate in the workshop "Future of GUAN" at the Tropospheric Research Institute in Leipzig, where the status and future of a German measurement network for ultrafine particles is discussed. During the workshop we will present our current work using GUAN data (e.g. Gerling, L., Löschau, G., Wiedensohler, A. and Weber, S., 2020. Statistical modelling of roadside and urban background ultrafine and accumulation mode particle number concentrations using generalized additive models. Science of The Total Environment, 703: 134570.)