Novel drugs, such as vaccines against covid-19, among others, are based on drug transport using nanoparticles. Whether this drug transport is negatively influenced by an accumulation of blood proteins on the nanoparticle’s surface was not clarified for a long time. Scientists at the Max Planck Institute for Polymer Research have now followed the path of such a particle into a cell using a combination of several microscopy methods. They were able to observe a cell-internal process that effectively separates blood components and nanoparticles.