Figure 1.

Comparison of volume electron microscopy techniques, for classical transmission EM (TEM) serial sectioning, consecutive ultrathin sections are collected on grids and imaged separately with TEM (a). For TEM-tomography thin sections (0.3–1 µm) are cut with a diamond knife, collected onto a grid, which is tilted relative to the TEM to 70°. After registration and back-projection, a tomogram is provided (b). For array-tomography serial sections are cut with a diamond knife, collected with an automated conveyor belt onto an adhesive tape (ATUMtome), mounted onto glass slides or silicon wafers and investigated with an scanning electron microscopy (SEM) (c). 3View®, the commercial version of the invention of W. Denk, manufactured by Gatan with a built-in ultramicrotome within the SEM. Serial sections are cut with a moving diamond knife and the block-face is imaged after every section (d). Focused ion beam (FIB)/SEM serial block-face milling is achieved by tilting a specimen in an SEM to 54°. An ion-gun is placed in the SEM at the same angle so that sections can be milled orthogonal to the specimen surface. Block-face images are taken at an angle of 36° with an SEM, and either backscattered electrons or secondary electrons are detected (e).