The Nanoparticle Conference in 2025 (NPC-25) is organized as an on-site conference at the ETH Zürich. It serves as an interdisciplinary platform for expert discussions on all aspects of nanoparticles, freshly emitted from various sources, transformed in ambient air, distributed on local and global scale, on technical mitigation aspects, particle legislation, and impact of particles on health, environment, and climate. The conference brings together representatives from research, industry and government.