EFCA’s 9^th Ultra Fine Particles (UFP) Symposium 2024 will again feature the most recent scientific progress and improve the dialogue with policy- and rule makers in Europe. The Symposium has gained visibility by its venue at the Baden-Württemberg State Representation in Brussels and attracts an effective mix of EU representatives and scientists. EFCA and KIT, together with GUS and CEEES are pleased to organize this event again.