Here's *an emphasis*.

A short one _a_ *b* .

Here's **a strong one**. 

Here's _one that uses underscores_. 

Here's __a strong one that uses underscores__.

This is not _ one _ neither is * this * neither is _ this_ neither is _this _.

An empty emphasis ** is not __ an emphasis.

A *multi-line
emphasis*

A **multi-line
strong emphasis**