Researchers have claimed that navels harbour an ecosystem of bacteria, which is similar in their biodiversity to the world's rainforests.
After two years of quite literal navel gazing, US researchers found 2,368 species of bacteria, 1,458 of which may be new to science, the Daily Mail reported.
Just eight of these species were found in more than 70 percent of individuals sampled.
However, questions remain as to what factors govern which species will be found on which people.
"The common, abundant species are from a relatively small number of evolutionary lines, indicating that they have evolved traits that make them at home on human skin," Rob Dunn of North Carolina State University said.
"However, we are still trying to figure out what determines which of these species are found in a given person's belly button.
"We've looked at sex, age, ethnicity and a number of other factors - none of them are predictive of which species live in that person," he said.
Dr Dunn and his team said that they have swabbed more than 500 belly buttons over the past two years, but concentrate on just 60 individuals for their study.
The researchers launched their project in part to investigate claims over recent years that the collection of organisms on human skin forms our first line of defence against pathogens.
"We know that without these microbes our immune systems won't function properly," Dr Dunn said in a statement.
"In fact, this collection of microbes must have a certain composition - must form a certain microbial ecosystem - in order for our immune system to function properly.
"This work is a significant step toward helping us understand which species are the most important players in those ecosystems," he said.
The study is published in the open-access journal PLoS One.