Children smudging their hands onto every available surface is normally gross and annoying -- unless, that is, the available surface in question is a sterile plate, which you then incubate in a petri dish.
The image was created by Tasha Sturm, who used sterile plates and tryptic soy agar to capture the handprint from her eight-year-old son after he had been playing outside. After incubating the plate for a day in a 37C incubator, and then leaving at room temperature for a few more, you get the wonderfully coloured flora and fungi you see above. [Microbe World via Kottke]
Picture: Tasha Sturm