Macro photographer Dariusz Pawlik of Poland posted this absolutely amazing photo of a single pollen on top of a fly's compound eye. Pawlik combined a stack of 229 individual photos to create the image you see above.
For reference, the lens (or ommatidium) of a fly's compound eye has a diameter of approximately 20 micrometer or 0.020 mm. A human's hair is approximately 50 micrometer thick.
Image: Dariusz Pawlik
Close-up image of that pollen on the eye of the fly.