Digitally-colorized scanning electron microscopic (SEM) image of a Giardia lamblia that was about to become two, separate organisms, as it was caught in a late stage of cell division, producing a heart-shaped form. This protozoan causes the diarrheal disease called giardiasis. Giardia species exist as free-swimming (by means of flagella) trophozoites, and as egg-shaped cysts. It is the cystic stage, which facilitates the survival of these organisms under harsh environmental conditions. The cyst is considered the infective form, and disease is often transmitted by drinking contaminated water (image by Dr. Stan Erlandsen, Center for Disease Control and Prevention, USA and obtained via the CDC Public Health Image Library, ID#11652); image modified by MIC. The cover is published under the Creative Commons Attribution (CC BY) license.