Oxygen plasma etching of entire block faces improves the resolution and usefulness of serial scanning electron microscopic images.

The oxygen plasma etching technique of Humphreys et al. has been modified and applied for use on the entire block face of methacrylate and epoxy embedded biological specimens. This technique greatly improves the visualization of tissue and cellular components, including intracellular organelles. This procedure, when coupled with the use of a miniature microtome which functions inside the SEM specimen chamber, greatly increases the usefulness of serial SEM images instead of serial sections for 3-dimensional reconstructions. Although this technique is demonstrated using the central nervous system of the nudibranch mollusc Hermissenda crassicornis and the squid (Loligo pealei) fin nerve on both osmicated and non-osmicated tissue, it should have broad applicability to most biological material.