Cysts of Giardia lamblia,stained with iron-hematoxylin (D, E) and in a wet mount (F; from a patient seen in Haiti). 

• Size: 8 to 12 µm in length.  

• These cysts have two nuclei each (more mature ones will have four).

Courtesy of the Division of Parasitic Diseases at the National Center for Infectious Diseases, Centers for Disease Control and Prevention