As researchers seek to understand high-level processes within living organisms, finer detail in three-dimensions of cell cultures and tissue needs to be observed using electron microscopy. Over the last several years, the Ga + focused ion beam (FIB) has been implemented for cross-sectioning resin-embedded samples to get an accurate representation of life science samples.[1-2] The Ga + FIB is capable of milling much finer slices (≥ 5 nm) of material than traditional sectioning methods. [3] When coupled with automated software packages, such as FEI’s Auto Slice and ViewTM and AmiraTM or AvizoTM, complete 3D-reconstructions of specimens are possible.[1-2] One limitation of the Ga + FIB is the moderate cross-section size prepared in a reasonable amount of time. The Xe + inductively-coupled plasma FIB is able to produce much larger cross-sections in faster time, while only sacrificing minimal prepared-surface quality. In this study, zebrafish specimens, prepared via osmium tetroxide staining and high pressure freezing followed by flat-embedding in epon resin, were used for evaluating and comparing the cross-sectioning capabilities of the Helios NanoLabTM Ga + and VionTM Xe+-based FIBs, and subsequent imaging, with respect to life science samples. Zebrafish (Danio rerio) are often used in biological studies due to their fast growth and regenerative abilities. The biological parallels with humans and the inexpensive cultivation of zebrafish make them attractive model organisms for large-scale studies.[4]