Cover picture: Computer representation of a human skin fibroblast as it exists in vivo (left and insets) and in vitro (right bottom). The shape of the cell is reconstructed from serial TEM images of human skin and optical microscopy of cultured cells, respectively. Microtubules are shown as thin yellow lines, endosomes in green, and lysosomes in red. For the sake of clarity, fewer organelles are shown in this rendition than were used in the simulation. Such a realistic reconstruction of cell geometry and organization was used by Dinh et al. to simulate the intracellular transport of synthetic gene vectors. Figure courtesy of Peter Allen, University of California, Santa Barbara. See the article by Dinh et al. on page 831.