Colloidal nanoparticles (NPs) are being developed for disease treatment and diagnosis (1), for example, as carriers for mRNA, agents that induce photothermal eradiation of prostate cancer, or contrast agents for magnetic resonance imaging (MRI). However, the use of NPs in clinical practice is still low. One limitation to their use is in delivering the NPs specifically to their target and to control when they are effective, and when they are cleared from the body. This is related to controlling their biodistribution (where the NPs go within the body) and pharmacokinetics (how local properties and dose change over time). Requirements vary depending on their application, but in general, improved biodistributions would reduce side-effects (for example, to off-target tissues) and improved pharmacokinetics would lower the required doses and reduce potential long-term toxicity (for ex-ample, through improved clearance). However, although most mechanisms of NP interaction with cells and tissues have been unraveled, the quantitative details are missing. In the talk several aspects on how such details could be quantitatively addressed will be presented. This involves the formation of the protein corona, the interplay between exocytosis and proliferation, and the development of new strategies for quantitative imaging.