Focused ion beam-scanning electron microscopy (FIB-SEM) CrossBeam analysis of polymorphonuclear neutrophils (PMNs) migrating through human choroid plexus papilloma cells (HIBCPP). FIB-SEM CrossBeam analysis demonstrates (A) paracellular- and (B) transcellular-migrating PMN through HIBCPP. (A) Multiple crosssections (orthoslices) through the three-dimensional images. The PMN is migrating paracellular through a widened intercellular space (marked with arrows) and squeezing between two cells. (B) The transcellular migrating PMN is distant to the intact tight junctions (TJs) and is surrounded by the cytoplasm of the HIBCPP cell. PE, plexus epithelial cell.