Expanding the parasite universe with expansion microscopy

Expansion microscopy (ExM) improves the effective resolution of a light microscope not by improving the microscope, but by physically enlarging the specimen. Parasitology, long constrained by the small size of its subjects, has embraced the technique with striking speed. In this article, we review how ExM, and in particular its ultrastructure-preserving derivative, ultrastructure expansion microscopy (U-ExM), has been applied across parasitology, from unicellular protozoa to multicellular helminths and arthropod vectors. We trace the rapid dominance of U-ExM, highlight the broad utility of antibody-free stains such as N-hydroxysuccinimide ester, and draw out the cytoskeleton and cell division as themes that recur across distantly related parasites. We close by identifying underexplored areas, potential challenges of the technique, and areas where we anticipate the technique will grow.