Who has more bacteria in their navel -Carl Zimmer of The Loom or Peter Aldhous of NewScientist? The swabs have been taken, and the cultures were grown. You can see the results in petri dishes. It's part of the Belly Button Biodiversity Project led by Jiri Hulcr of North Carolina State University.

The project was conceived as a device to interest the public in microbiology, and to counter the common view that bacteria are nothing but causes of disease. "This fear is based on a lack of awareness that we live in a microbial world," says Hulcr, who notes that even some "self-described germophobes" have confronted their anxieties and given swabs.

Hulcr also aims to extend a scientific frontier: researchers are realising that the human "microbiome" - the diversity of microorganisms that inhabit our bodies - is a key influence on our health and physiology. The skin remains poorly explored territory, and the belly button is an ideal sampling point because it doesn't get as scrubbed and sprayed with chemicals as much other, more accessible parts.