3D electron microscopy is a technique that builds three-dimensional images of biological specimens at nanometer resolution. The primary methods used in 3DEM include Serial Block-Face Scanning Electron Microscopy (SBF-SEM), Focused Ion Beam Scanning Electron Microscopy (FIB-SEM), and Electron Tomography. These techniques involve sequentially imaging thin slices of a specimen and reconstructing the images into a 3D model.