Organoids embedded in resin were mounted onto an aluminum pin with a cyanoacrylate adhesive. The pin, which takes the place of a normal SEM stub, was loaded into a sample holder for the Gatan 3View (Gatan Inc., Pleasanton, Ca). Serial block face scanning electron microscopy was carried out as previously described (Denk and Horstmann, 2004). Data was collected using an FEI Quanta 600 FEG SEM; serial images were 4k x 4k and acquired at 5 kV; z-dimension slices of 50 nm. 3D volume representations of the data were prepared using CHIMERA(Pettersen et al., 2004). CHIMERA was used to perform manual segmentation of membranes and to display the 3-dimensional volumes.