Shown are trophozoites of Naegleria fowleri in a Giemsa-stained cytospin preparation of cerebrospinal fluid. This is a critical result that should be reported to the clinical team immediately, since N. fowleri causes a rapidly-fatal meningoencephalitis. The trophozoites have abundant bubbly cytoplasm and a small round-to-oval nucleus with a large blot-like karyosome.