- 资料原文
But there is one question about the belly button that all people around the world ask.
Have you ever observed a little ball of fluff or soft material in your belly button? This is belly button fluff. Belly button fluff is especially common in innie belly buttons. Have you ever wondered how it gets there? Have you ever wondered what it is made of? These are questions that people everywhere ask. And many people - scientists and others - have tried to find the answers.
- 中文译文
