Capillary condensation on fractal soot in the atmosphere. Under realistic atmospheric conditions, soot particles are exposed to multiple condensing chemicals that are present at significantly lower concentrations than in our laboratory experiments. To assess the role of capillary condensation on soot in the atmosphere, we extended our model towards multi-component vapors (Supplementary section 8). We then used this multi-component capillary condensation model (MCCCM) in conjunction with the particle-resolved PartMC-MOSAIC aerosol model to explore relevant atmospheric scenarios. Here we illustrate our findings using a remote atmosphere scenario, because in a polluted urban atmosphere the condensation of highly supersaturated sulfuric acid can mask the contribution from capillary condensation of subsaturated organic vapors.