Navel lint: From Wikipedia:
Navel lint, or more commonly belly button lint or navel fluff, is an accumulation of fluffy fibres in one’s navel.
Many people find that, at the beginning and end of the day, a small lump of fluff has appeared in the navel cavity. The reasons for this have been the subject of idle speculation for many years but in 2001, Dr. Karl Kruszelnicki of the University of Sydney, Australia undertook a systematic survey to determine the ins and outs of navel lint. His primary findings were as follows:
Dr. Kruszelnicki was awarded the Ig Nobel Prize for Interdisciplinary Research in 2002.
David Hamilton, a Toronto native, has been an avid belly button lint enthusiast for years. Travelling to many different conferences and conventions worldwide, David has become the world’s foremost expert and now holds the largest private collection of Human Navel Lint. He is currently working on developing his thesis on the nutritional benefits of ingesting navel lint.
Graham Barker of Perth, Western Australia, is in the Guinness Book of Records as the record holder for collecting navel lint. He has been collecting navel lint almost every day for over 20 years since 17th January 1984. He collects about 3.03 mg per day. Contrary to the research of Dr. Kruszelnicki, his lint is in a particular shade of red, even though he rarely wears red clothes.