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:
Navel lint is mostly stray fibers from one's clothing, mixed with some dead skin cells, and body hair.
The lint comes from a person's shirt or top. The fibers move there from friction of body hair.
Women have less navel lint because of their finer and shorter body hair. Older men have it more because they have more hair and it is thicker.
Navel lint's color is usually blue-gray. The color is most likely an average of all clothing colors worn.
Navel lint is entirely harmless and does not need to be corrected.
Dr. Kruszelnicki was awarded the Ig Nobel Prize 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.
References
Other websites
World record navel lint collection by Graham Barker
Fibers