How Do I Use A Small Font Size In Questions And Answers?

Is there any way to use a small font size in questions or answers? That is, for the purpose of minor and possibly irrelevant information?

I've checked the Markdown syntax but couldn't find anything. However, I feel I've seen it on the site somewhere...I have seen a website Fonts Monster in which I see very different types of font styles but I can't find the smallest font in this very type of font but.......