These are some cells from a plant root that has formed a symbiosis with a mycorrhizal fungus. The dark blue ribbon-shaped structures are fungal hyphae that have been stained with trypan blue.

You can see that the hyphae form several coils that look like a bow. This curling of hyphae inside the root cell increases the surface area at which the plant and fungus can exchange nutrients.

You can also see a xylem element with corkscrew-like wall thickenings in the vicinity of the root cell with the fungal structures. How the fungus recognizes the appropriate root cells to invade and how the plant recognizes beneficial mycorrhizal fungi is currently an active area of research.