Nano-sized objects exist as engineered tools as well as natural or anthropogenic environmental factors. Recent progress in the field of nanotechnology allows for a deeper understanding of their impact on organisms. Recently, we showed that the size-dependent cell interaction with quantum dots is autophagy-mediated. The potential role of other endo- and exogenous nanoparticles in terms of autophagy is discussed here. Their physical properties should be taken into consideration while constructing delivery systems. Furthermore, we propose several models of targeted nanoparticles delivery. Autophagy can be considered as an additional mechanism providing intracellular selectivity for introduced nanoparticles. Addendum to: Quantum Dots for Human Mesenchymal Stem Cells Labeling. A Size-Dependent Autophagy Activation O. Seleverstov, O. Zabirnyk, M. Zscharnack, L. Bulavina, M. Nowicki, J.M. Heinrich, M. Yezhelyev, F. Emmrich, R. O’Regan and A. Bader Nano Lett 2006; 12:2826-32