Several Giemsa-stained trophozoites are shown here from in vitro culture (1000x magnification). They measure 7 to 30 micrometers in greatest dimension and have a round/oval to piriform (pear) shape. Note the characteristic large nucleus (usually found at the broader end) and flagella. They have 4 anteriorly directed flagella and one posterior-facing flagellum that lies along the outer edge of the undulating membrane.