TEM images illustrating the process of QD cellular uptake and intracellular translocation. a. QD endocytosis through plasma membrane invagination. Black arrows point to QDs attached to the cell surface; the white arrow denotes the membrane pit engulfing QDs. b. QDs sequestered and dispersed in early endosomes (white arrow). c. QDs condensed in late endosomes/lysosomes (white arrow).