FIB-SEM volumes of pancreatic β cells and 3D segmentation of microtubules and organelles. (A) Full FIB-SEM volume of a pancreatic islet (left), one of which was acquired for low- and high-glucose conditions containing three (low) and four (high) complete β cells (right). Shown are the lateral (x-y) and axial (x-z) views of a small crop, highlighting the quasi-isotropic resolution of the FIB-SEM volumes. The arrowhead indicates a microtubule, the asterisk an insulin SG. Scale bar, 500 nm. (B) Raw lateral images with segmentation overlay for insulin SGs, mitochondria, Golgi apparatus, nucleus (of the identical region), and microtubules and centrioles (of different regions). Below the overlays, we show 3D renderings of the corresponding organelles of one whole cell (high-glucose condition) accompanied by a transparent rendering of the plasma membrane. Centrioles are magnified in the last panel. Scale bars, 500 nm. (C) 3D rendering of one cell containing all segmented organelles. The plasma membrane and insulin SGs were removed in the left half of the cell to help visualize its inner parts.