This animation explains the accumulation of conventional anticancer drugs and polymeric micelles in normal and cancerous tissues. The conventional anticancer drugs penetrate the vascular wall and therefore accumulate in both normal and cancerous tissues. Such non-specific accumulation results in limited drug efficacy and occurrence of side effects. In contrast, polymeric micelles cannot penetrate the vascular wall and they only pass through leaky tumor vasculature. Note that tumor vasculature possesses the pore of several tens to hundreds nanometer. Therefore, polymeric micelles can selectively accumulate in solid tumors, achieving enhanced drug efficacy without side effects. This video relates to an article that appeared in the Jan. 5, 2011, issue of Science Translational Medicine, published by AAAS. The study, by Mami Murakami of the University of Tokyo in Tokyo, Japan, and colleagues was titled, "Improving Drug Potency and Efficacy by Nanocarrier-Mediated Subcellular Targeting."