This is a layer of epithelial cells that was subjected to sever freeze-thaw cycles before being imaged at 400x magnification, which caused the membranes to rupture and form these arrays of crystal-like structures. When frozen, the water inside the cells expands, breaking through the cell membrane. With the membrane integrity compromised, when the cells are thawed the water inside leaks out, the fragments of membrane form aggregates, and cell structure is lost. This is why frozen meat can take on a mushy texture, or why severe frostbite results in the death of the skin.
Artwork contributed by Don Pottle.