This is a scanning electron micrograph (SEM) of an in vitro Giardia lamblia culture, which had been cultivated in bile-free TYI-S-33 medium for 48 hrs, then incubated 24 hrs with 10 mg/ml bovine bile in order to stimulate cyst formation. This photograph contains both trophozoites, and a cluster of maturing cysts (bottom right). At far left, the two trophozoites-staged organisms are positionally situated opposite to one another, with the farthest left G. lamblia displaying its dorsal, or u