Do you ever find little fluffs of lint trapped in your bellybutton? What is that stuff, and where does it come from? Dr. Karl Kruszelnicki, a physicist from the University of Sydney was on an Australian public radio show when a listener called in to ask these same questions. “Dr. Karl” realized that no one actually knew the answers, and set out to investigate this fuzzy phenomenon. His team surveyed nearly 5,000 men and women from all over the world about their bellybutton lint, and their age, sex, body hair, body shape, clothing type, and several other factors that could influence lint formation.