On my way to school, I started to think how clean is defined. When we say someone is clean, it often means that the person smells good, looks tidy and behaves in a polite way. But the overall definition is too vague that it actually and mostly depends on people's personal feelings rather than their optional thoughts. So to what extent one should reach can we call him clean? I have no idea yet. What's more, another simple but more detailed question jumped in my head. Bathing is often the method that we make sure we are "clean". But we still don't have a scientific and precise way to determine how one baths can lead to a clean human-being. In our daily life, we bath in the way we were bathed at an early age. The way we usually bath seem to have a lot of science behind it. It in fact totally relies on personal experiences which I don't trust very much. So how can we make sure that we take a clean bath? I'm still wondering...