From the Smithsonian website:

Once you’ve picked your jaw from the floor, here’s what you’re looking at: the final stop of this zoom, which spans multiple orders of magnitude, is a little bacterium. That bacterium is resting on a diatom, a class of algae that are known for their silica shells. The diatom is, in turn, sitting on an amphipod, a type of shell-less crustacean.

Reddit’s adamwong246 said it best, “There’s a bacterium on a diatom on an amphipod on a frog on a bump on the log in the hole in the bottom of the sea!”

The animated gif was made by James Tyrwhitt-Drake using a scanning electronic microscope at the University of Victoria’s Advanced Microscopy Facility. Tyrwhitt-Drake runs the blog Infinity Imagined.