A spatio-temporal mapping of the uptake of silica (SiO(2)) nanoparticles of different sizes by lung epithelial cells has been obtained. Based on high control of nanoparticle dispersion in cell media and cell exposure, one obtains reproducible and quantitative time-resolved data using a combination of flow cytometry, fluorescence and electron microscopies. We are thereby able to give a rather detailed account of the journey of SiO(2) nanoparticles from the early events of uptake to their final sub-cellular localization.