Navel lint

Navel lint, also called belly button lint, belly button fluff or navel fluff, is a collection 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. People have wondered why this happens for many years. In 2001, Dr. Karl Kruszelnicki of the University of Sydney, Australia, did a survey to find out why this happens. This is what he found out:
Dr. Kruszelnicki was awarded the for Interdisciplinary Research in 2002. The Ig Nobel Prize is given for "achievements that cannot or should not be repeated".
Austrian scientist Georg Steinhauser has also done research on the navel lint.