Cystic and tubular epithelia in vivo and in vitro share the same topological distribution. Confocal optical sections from fixed and stained whole-mount embryonic mouse kidney and lung tissues enable direct comparison of topological distributions. Representative mid, top, or bottom sections and the relative segmentation are shown for the three tissue types we analyzed. (A, left) Midsection of an E13.5 lung alveolar tip stained with E-cadherin (green) and DAPI (blue). (A, right) Bottom section (top) and corresponding segmentation (bottom) with E-cadherin staining only. Number of segmented cells in the image: 96. (B) Midsection of developing ureteric tubule in an E13.5 mouse stained with E-cadherin (left), bottom section (middle), and corresponding segmentation (right). Number of segmented cells in the image: 88. (C) Tip of a developing ureteric tree in the kidney of an E13.5 mouse, stained with E-cadherin (green) and DAPI (blue; left), together with a top section (top right), and corresponding segmentation (bottom right). Number of segmented cells in the image: 60. (D) Normalized topological distributions were reconstructed for three different lung tissue samples and four kidney tissue samples. All samples follow the nonequilibrium theoretical distribution. For the sake of comparison, the corresponding equilibrium topological distribution is shown. Bars, 10 µm.