Cover picture: A 3 × 3 × 3 3D array of Pseudomonas aeruginosa bacteria. (Top left) A transmission micrograph of three overlapping 3 × 3 arrays of P. aeruginosa, shifted by 3 µm from each other along the optical (z) axis and embedded in hydrogel. The corner vertex of each of the arrays is highlighted by a blue, green, and red circle in the figure. The focus is coplanar with the middle of the three arrays so that the underfocused top array (blue) appears bright whereas the overfocused bottom array (red) appears to be dark relative to the center array (green). The three arrays are shifted by 4 µm along both the x and y axes to facilitate imaging. (Top right) A false-color isosurface, reconstructed from volumetric data obtained from a series of confocal images, showing the offset along x and y axes with the xy-projection. (Bottom left) Reconstructed (false color) isosurface xz-projection, illustrating the 3 µm separation along z axis. (Bottom right) A false-color isosurface perspective reconstruction illustrating the top (blue), middle (green), and bottom (red) arrays separated by 2 µm. See the article by Akselrod et al. on page 3465.