Hourglass cells (HGC) are prominent cells in the legume seed coat. Miller et al. (pp. 235–242) document HGC development in soybean, Glycine max, and relate structural changes to expression of an HGC-specific soybean peroxidase (SBP). SBP protein and activity are detectable in HGCs before differentiation is complete; furthermore, activity appears vacuolar, as predicted. These results provide a basis for biotechnology aimed at protein targeting to components of the HGC endomembrane systems.