This image depicts Giardia lamblia trophozoites on a commercially prepared slide of fecal material as seen at x1,000 in a bright-field microscope. G. lamblia is a pathogen found worldwide which infects humans through consumption of impure water containing Giardia cysts.

Giardia moves with flagella. Each troph is a bilaterally symmetrical pear-shaped flagellate usually possessing two nuclei. Each nucleus contains a central karyosome that resembles eyes on a face. An axostyle, resembling a dark line through the center of the cyst, may be visible. Parabasal bodies may also appear as comma-shaped structures.

The average size range of this organism is 10 to 20 µm.