English:Hyphea of Hyaloperonospora parasitica (downy mildew) growing within the leaf of a compatible (susceptible) Arabidopsis thaliana (cf.wikipedia) observed by bright-field microscopy. The staining with trypan blue makes the cytoplasm of H. parasitica dark blue. The long structure is the hyphea, whereas the little sphere are haustoria. This is the vegetative step of the short life cycle of H. parasitica.